LSAT Logical Reasoning: Strengthen and Support Questions — Questions and Answers

Question 1: A scientist argues that a newly discovered bacterium causes a specific skin disease because patients with the disease all test positive for the bacterium. Which of the following, if true, most strengthens this argument?

The bacterium was discovered in a research laboratory.
Healthy individuals without the skin disease consistently test negative for the bacterium. (Correct answer)
The skin disease affects approximately 2% of the population.
The bacterium is similar in structure to other known pathogens.
The disease has been observed in multiple countries.

Correct answer: Healthy individuals without the skin disease consistently test negative for the bacterium.

Establishing that healthy people test negative (completing the necessary correlation pattern) significantly strengthens the causal claim by showing the bacterium and disease co-occur and co-absent.

Koch's postulates require that the organism be absent from healthy individuals. Answer B completes this criterion: the bacterium appears in sick patients and is absent in healthy ones, creating a strong positive correlation in both directions. This biconditional relationship (disease ↔ bacterium) substantially strengthens the causal hypothesis.

Question 2: A city argues that its new after-school tutoring program increased graduation rates, pointing to a rise from 78% to 85% graduation rate after implementation. Which of the following most strengthens this argument?

The tutoring program employed certified teachers.
Neighboring cities without similar programs showed no comparable improvement in graduation rates during the same period. (Correct answer)
The program served 300 students in its first year.
Tutoring has been shown to improve academic confidence.
The program was funded by a federal education grant.

Correct answer: Neighboring cities without similar programs showed no comparable improvement in graduation rates during the same period.

A comparison group showing no improvement rules out external factors (economic conditions, demographic shifts) as alternative explanations, strengthening the inference that the program caused the improvement.

The argument's weakness is that the graduation improvement could reflect factors unrelated to the program (economic recovery, demographic change). Answer B provides a quasi-experimental control: if similar cities saw no improvement during the same period under the same external conditions, the program is the most plausible cause of the city's improvement.

Question 3: A nutritionist argues that a specific probiotic supplement improves digestive health in adults with irritable bowel syndrome (IBS). Which of the following most strengthens this argument?

The probiotic was developed by a team of gastroenterologists.
In a randomized controlled trial, IBS patients taking the probiotic reported significantly fewer symptoms than those receiving a placebo. (Correct answer)
Probiotics are generally recognized as safe by regulatory agencies.
The supplement contains five distinct bacterial strains.
IBS affects millions of people worldwide.

Correct answer: In a randomized controlled trial, IBS patients taking the probiotic reported significantly fewer symptoms than those receiving a placebo.

A randomized controlled trial with a placebo group is the gold standard for establishing causation, directly supporting the effectiveness claim with rigorous evidence.

Randomized controlled trials with placebo controls eliminate confounding variables and placebo effects, providing the strongest evidence for causal claims about treatment efficacy. Answer B describes exactly this design, directly supporting the claim that the supplement—not other factors—causes the improvement in IBS symptoms.

Question 4: An archaeologist argues that a coastal settlement was abandoned due to rising sea levels, rather than warfare or disease. Which of the following most strengthens this argument?

The settlement shows signs of rapid abandonment rather than gradual decline.
Sediment core samples from the region show evidence of rapid sea-level rise occurring precisely at the time of the abandonment, with no evidence of mass casualties or violent destruction. (Correct answer)
Similar settlements in the same era were also abandoned.
The inhabitants of the settlement were skilled fishermen.
Historical records from the period are incomplete.

Correct answer: Sediment core samples from the region show evidence of rapid sea-level rise occurring precisely at the time of the abandonment, with no evidence of mass casualties or violent destruction.

Geological evidence directly confirming sea-level rise at the abandonment date, combined with absence of warfare/disease evidence, supports the specific causal claim over the alternatives.

The archaeologist needs to establish sea-level rise as the cause and rule out competing explanations. Answer B does both simultaneously: sediment cores confirm the timing of sea-level rise (supporting the proposed cause) while the absence of casualties or destruction evidence undermines the warfare and disease alternatives. This dual confirmation-and-elimination strengthens the argument maximally.

Question 5: A health researcher argues that moderate coffee consumption (2-3 cups daily) reduces the risk of type 2 diabetes. Which of the following most strengthens this argument?

Coffee is one of the most widely consumed beverages globally.
A mechanism has been identified: compounds in coffee improve insulin sensitivity by activating specific cellular receptors. (Correct answer)
Type 2 diabetes rates have been rising globally.
The research was funded by an independent health foundation.
People who drink coffee tend to be more socially active.

Correct answer: A mechanism has been identified: compounds in coffee improve insulin sensitivity by activating specific cellular receptors.

Identifying a specific biological mechanism (how coffee affects insulin receptors) provides a plausible causal pathway, substantially strengthening the correlation between coffee consumption and reduced diabetes risk.

Correlational evidence is strengthened when a plausible biological mechanism explains how the cause produces the effect. Answer B provides exactly this: a specific receptor-level mechanism linking coffee compounds to insulin sensitivity. This mechanistic evidence transforms the statistical association into a biologically grounded causal claim.

Question 6: A geologist argues that a particular rock formation was created by a massive ancient volcanic eruption rather than gradual sedimentary processes. Which of the following most strengthens this argument?

Volcanic rock formations can be visually similar to sedimentary formations.
The rock formation contains minerals that can only form under the extreme heat and pressure conditions produced by volcanic eruptions, not sedimentary processes. (Correct answer)
The formation is located near a known ancient volcanic region.
Geologists have studied similar formations for decades.
Rock dating methods have become increasingly precise.

Correct answer: The rock formation contains minerals that can only form under the extreme heat and pressure conditions produced by volcanic eruptions, not sedimentary processes.

Minerals that can only form under volcanic conditions provide direct chemical evidence for volcanic origin, ruling out sedimentary formation processes.

The geologist's argument requires distinguishing between two competing formation processes. Answer B provides a diagnostic marker: minerals uniquely produced by volcanic conditions serve as chemical fingerprints that directly confirm volcanic origin and simultaneously rule out sedimentary processes, providing strong support for the conclusion.

Question 7: A social scientist argues that income inequality causes social unrest, citing a correlation between higher inequality (measured by Gini coefficient) and greater political instability across countries. Which of the following most strengthens this argument?

The Gini coefficient is a commonly used measure of income distribution.
Historical analysis shows that periods of increasing inequality in stable societies are reliably followed by increases in social unrest, before external factors changed. (Correct answer)
Some highly unequal countries have remained politically stable for decades.
Political scientists disagree about the causes of social unrest.
International organizations track income inequality data annually.

Correct answer: Historical analysis shows that periods of increasing inequality in stable societies are reliably followed by increases in social unrest, before external factors changed.

Temporal sequencing (inequality increases followed by unrest increases) within societies provides stronger causal evidence than cross-sectional correlation, and the phrase 'before external factors changed' helps rule out reverse causation.

Cross-sectional correlations face many confounds. Answer B provides longitudinal evidence within societies over time, establishing temporal precedence (inequality precedes unrest) and controlling for stable country-level factors. This within-country, over-time pattern is much stronger causal evidence than the cross-national correlation alone.

Question 8: A pharmaceutical researcher argues that a new antibiotic is effective against a drug-resistant bacterial strain. Which of the following most strengthens this argument?

The antibiotic was developed using a novel molecular targeting approach.
Laboratory tests show the antibiotic kills the resistant strain at low concentrations, and animal trials show complete infection clearance with no evidence of new resistance developing. (Correct answer)
Drug-resistant bacteria pose a major threat to public health.
The research team has published studies on antibiotic resistance.
Previous antibiotics have failed against this bacterial strain.

Correct answer: Laboratory tests show the antibiotic kills the resistant strain at low concentrations, and animal trials show complete infection clearance with no evidence of new resistance developing.

Laboratory efficacy data plus animal trial success and absence of new resistance development provides multi-layered evidence directly supporting both effectiveness and durability of the treatment.

Answer B provides three distinct pieces of evidence: (1) in vitro efficacy at low concentrations shows potency; (2) animal trial success shows in vivo effectiveness; (3) no resistance development addresses the durability concern. This converging multi-level evidence provides comprehensive support for the effectiveness argument.

Question 9: An economist argues that trade liberalization increases economic growth in developing countries. Which of the following most strengthens this argument?

Trade liberalization involves reducing tariffs and import quotas.
Countries that liberalized trade showed accelerated GDP growth in the years following liberalization, while those that did not liberalize showed no comparable growth acceleration despite similar starting conditions. (Correct answer)
Some economists oppose free trade agreements.
Developing countries face many economic challenges beyond trade policy.
International trade volumes have increased substantially over the past 50 years.

Correct answer: Countries that liberalized trade showed accelerated GDP growth in the years following liberalization, while those that did not liberalize showed no comparable growth acceleration despite similar starting conditions.

A quasi-experimental comparison showing that liberalizing countries grew faster than non-liberalizing countries with similar starting conditions provides strong causal evidence for the economic growth claim.

Answer B provides a natural experiment: countries that liberalized are compared with similar countries that did not, with both groups experiencing the same global economic environment. Acceleration in liberalizing countries but not comparable non-liberalizing countries makes trade policy the most plausible cause of the differential growth.

Question 10: A psychologist argues that cognitive behavioral therapy (CBT) is more effective than medication alone for treating panic disorder. Which of the following most strengthens this argument?

CBT helps patients identify and challenge irrational thought patterns.
In a study where panic disorder patients were randomly assigned to CBT, medication, or combined treatment, CBT patients showed lower relapse rates at 12-month follow-up than medication-only patients. (Correct answer)
Panic disorder is characterized by recurring unexpected panic attacks.
CBT requires more sessions than medication management.
Many therapists are trained in CBT techniques.

Correct answer: In a study where panic disorder patients were randomly assigned to CBT, medication, or combined treatment, CBT patients showed lower relapse rates at 12-month follow-up than medication-only patients.

A randomized study with long-term follow-up showing lower relapse rates directly addresses both the comparative efficacy claim and demonstrates durable advantage for CBT over medication alone.

Answer B provides randomized comparison with active control (medication) and long-term outcome data. The randomization eliminates selection bias; the 12-month follow-up captures relapse rates that reflect durable treatment effects rather than acute symptom suppression. This addresses the comparative superiority claim more directly than any mechanistic or correlational evidence.

Question 11: A wildlife biologist argues that sea otter populations control sea urchin numbers, which in turn protects kelp forests. Which of the following most strengthens this argument?

Sea otters are a keystone species in Pacific coastal ecosystems.
In areas where sea otters were hunted to near-extinction, sea urchin populations exploded and kelp forests disappeared, and when otters were reintroduced, urchin numbers declined and kelp forests recovered. (Correct answer)
Kelp forests provide habitat for many marine species.
Sea otters consume up to 25% of their body weight in food daily.
Conservation efforts have successfully increased sea otter populations in some areas.

Correct answer: In areas where sea otters were hunted to near-extinction, sea urchin populations exploded and kelp forests disappeared, and when otters were reintroduced, urchin numbers declined and kelp forests recovered.

The natural experiment of otter removal causing kelp collapse and otter reintroduction causing kelp recovery provides strong before-after-during evidence for the trophic cascade the biologist describes.

Answer B describes a natural experiment with both a removal phase and a reintroduction phase, providing reciprocal evidence: otter removal → urchin explosion → kelp collapse; otter reintroduction → urchin decline → kelp recovery. This bidirectional, replicated pattern across areas is very strong evidence for the causal chain.

Question 12: An environmental scientist argues that reducing vehicle emissions in urban areas will improve residents' respiratory health. Which of the following most strengthens this argument?

Vehicle emissions contain particulate matter and nitrogen oxides.
Cities that implemented strict emission reduction zones showed measurable decreases in asthma hospitalizations and respiratory illness rates in the years following implementation. (Correct answer)
Air quality monitoring technology has improved significantly.
Some vehicle manufacturers have voluntarily reduced emissions.
Urban populations are larger than rural populations.

Correct answer: Cities that implemented strict emission reduction zones showed measurable decreases in asthma hospitalizations and respiratory illness rates in the years following implementation.

Empirical data from cities that implemented emission reductions showing direct decreases in respiratory health outcomes provides real-world validation of the proposed causal pathway.

Answer B provides observational outcome data from real-world policy implementations: emission reductions were followed by measurable health improvements. This before-after comparison in cities that changed policy provides direct evidence linking emission reduction to respiratory health improvement, supporting the argument with real-world evidence.

Question 13: A linguist argues that early childhood bilingualism enhances executive function (cognitive control) compared to monolingual upbringing. Which of the following most strengthens this argument?

Bilingual children switch between two language systems constantly.
In laboratory tasks measuring cognitive control, bilingual children who have used both languages since birth perform significantly better than monolingual peers matched for age, socioeconomic status, and IQ. (Correct answer)
Many countries have bilingual educational systems.
Language acquisition occurs most easily in early childhood.
Executive function skills predict academic success.

Correct answer: In laboratory tasks measuring cognitive control, bilingual children who have used both languages since birth perform significantly better than monolingual peers matched for age, socioeconomic status, and IQ.

Controlled laboratory comparison with socioeconomic status and IQ matching eliminates key confounders, directly measuring the specific cognitive advantage claimed.

Answer B addresses the main confounders in bilingual cognitive research (SES and general intelligence) by matching comparison groups. If groups matched on these dimensions still show executive function differences favoring bilinguals, the remaining explanation is the bilingualism itself, providing strong support for the cognitive advantage claim.

Question 14: A public health researcher argues that restricting fast food advertising during children's television programming will reduce childhood obesity rates. Which of the following most strengthens this argument?

Children are exposed to thousands of food advertisements annually.
Countries that implemented such advertising restrictions showed significantly lower rates of childhood obesity increase compared to countries that did not implement restrictions during the same period. (Correct answer)
Obesity is associated with numerous health complications.
Fast food companies spend billions on advertising each year.
Parental education about nutrition has been shown to affect children's eating habits.

Correct answer: Countries that implemented such advertising restrictions showed significantly lower rates of childhood obesity increase compared to countries that did not implement restrictions during the same period.

Cross-national comparison showing lower obesity growth in countries with advertising restrictions versus comparable countries without restrictions provides quasi-experimental evidence supporting the causal claim.

Answer B provides a natural experiment: countries with restrictions versus without restrictions during the same time period. If restricting countries showed lower obesity growth rates despite facing the same global trends in fast food availability, the advertising restriction is the most plausible explanatory difference, supporting the public health argument.

Question 15: A historian argues that the development of the printing press was the primary cause of the Protestant Reformation, because it enabled mass distribution of reformist ideas. Which of the following most strengthens this argument?

Gutenberg developed the printing press around 1440.
Reformist ideas very similar to those of Luther and Calvin existed for centuries before the Reformation but failed to spread widely, while the same arguments printed and distributed after 1450 reached mass audiences within weeks. (Correct answer)
Luther posted his 95 Theses in 1517.
The Catholic Church was powerful and wealthy in the 15th century.
Printing technology spread across Europe within decades of its invention.

Correct answer: Reformist ideas very similar to those of Luther and Calvin existed for centuries before the Reformation but failed to spread widely, while the same arguments printed and distributed after 1450 reached mass audiences within weeks.

The historical comparison shows that the ideas themselves were not new—distribution technology was the differentiating factor, directly supporting the printing press as the primary enabling cause.

Answer B provides a powerful historical comparison: similar ideas existed pre-printing press but failed; those same arguments succeeded post-printing press. This controls for the content of the ideas and isolates the printing press as the variable that changed. If the ideas themselves aren't new but their distribution technology changed, the technology is the most plausible causal factor.

Question 16: A criminal justice researcher argues that community-based rehabilitation programs reduce recidivism more effectively than incarceration. Which of the following most strengthens this argument?

Rehabilitation programs focus on vocational training and mental health treatment.
When similar offenders were randomly assigned to community programs versus incarceration, those in community programs had significantly lower re-arrest rates over a 5-year follow-up period. (Correct answer)
Incarceration costs taxpayers significantly more than community supervision.
Many formerly incarcerated individuals struggle to find employment.
Community programs have operated in several cities for over a decade.

Correct answer: When similar offenders were randomly assigned to community programs versus incarceration, those in community programs had significantly lower re-arrest rates over a 5-year follow-up period.

Random assignment eliminates selection bias (the concern that lower-risk offenders are systematically placed in community programs), providing strong causal evidence that community programs reduce recidivism.

The major challenge in recidivism research is selection bias: community programs may select lower-risk offenders who would reoffend less regardless of program. Answer B eliminates this confound through randomization—similar offenders randomly assigned to different conditions, with community program participants showing lower recidivism. This directly addresses the causal claim.

Question 17: An agricultural scientist argues that crop rotation improves soil health and increases yields over time compared to monoculture farming. Which of the following most strengthens this argument?

Different crops absorb and return different nutrients to the soil.
Long-term experimental plots randomly assigned to crop rotation versus continuous monoculture show progressively widening yield gaps over 10+ years, with rotation plots maintaining consistent yields while monoculture plots decline. (Correct answer)
Organic farmers commonly practice crop rotation.
Soil health can be measured by microbial diversity and nitrogen content.
The practice of crop rotation dates back thousands of years.

Correct answer: Long-term experimental plots randomly assigned to crop rotation versus continuous monoculture show progressively widening yield gaps over 10+ years, with rotation plots maintaining consistent yields while monoculture plots decline.

Long-term randomized experimental data showing diverging yield trajectories provides the strongest evidence that rotation specifically causes sustained soil health and yield advantages.

Answer B provides randomized long-term experimental evidence—the most rigorous design. The progressive widening of yield gaps over 10+ years is especially compelling because it shows the cumulative soil health effect over time, not just short-term differences. Randomization eliminates initial soil quality differences as a confound.

Question 18: A tech analyst argues that user interface simplicity increases app adoption rates, citing successful minimalist apps. Which of the following most strengthens this argument?

Minimalist design principles have been popularized by Apple and Google.
A/B testing of identical app features with simple versus complex interfaces showed significantly higher adoption and retention rates for the simple interface across multiple demographic groups. (Correct answer)
Many users abandon apps they find confusing.
Interface design is a specialized field with established principles.
User experience research is routinely conducted by technology companies.

Correct answer: A/B testing of identical app features with simple versus complex interfaces showed significantly higher adoption and retention rates for the simple interface across multiple demographic groups.

Controlled A/B testing isolates interface complexity as the variable and demonstrates its causal effect on adoption across diverse groups, providing the strongest evidence for the claim.

Answer B describes the ideal experiment for this claim: A/B testing holds all features constant while varying only interface complexity, isolating the causal effect of simplicity. Multiple demographic groups increase generalizability. Higher adoption and retention rates in the simple condition provide direct causal evidence for the interface-adoption relationship.

Question 19: A climate scientist argues that ocean acidification caused by CO2 absorption is harming coral reef ecosystems. Which of the following most strengthens this argument?

Oceans absorb approximately 30% of human-produced CO2 emissions.
Controlled aquarium experiments exposing coral to seawater with elevated CO2 concentrations show measurably reduced calcification rates and skeletal weakening at concentrations already observed in some ocean regions. (Correct answer)
Coral reefs support approximately 25% of marine biodiversity.
Ocean temperatures have been rising alongside acidification.
Some coral species appear more resilient to acidification than others.

Correct answer: Controlled aquarium experiments exposing coral to seawater with elevated CO2 concentrations show measurably reduced calcification rates and skeletal weakening at concentrations already observed in some ocean regions.

Controlled experiments demonstrating the specific biological mechanism at CO2 concentrations already present in some ocean regions provides strong causal evidence linking acidification to coral harm.

Answer B provides controlled experimental evidence that isolates CO2 concentration as the causal variable and demonstrates measurable biological harm (reduced calcification) at ecologically relevant concentrations. The detail that these concentrations already exist in some ocean regions bridges laboratory findings to real-world relevance, strengthening the argument's applicability.

Question 20: A sociologist argues that strong social networks improve mental health outcomes for elderly individuals living alone. Which of the following most strengthens this argument?

Social isolation is a recognized risk factor for depression.
Elderly individuals who received systematic social visitation programs showed significantly lower rates of depression and cognitive decline at 2-year follow-up compared to matched controls who did not receive the programs. (Correct answer)
Many elderly people lose social connections after retirement.
Depression treatment options are available for elderly patients.
Community centers can provide social opportunities for isolated individuals.

Correct answer: Elderly individuals who received systematic social visitation programs showed significantly lower rates of depression and cognitive decline at 2-year follow-up compared to matched controls who did not receive the programs.

An intervention study with matched controls and long-term follow-up directly tests whether providing social connections (not just having them) causally improves mental health outcomes.

Answer B describes a quasi-experimental intervention study: systematic social visitation was provided to one group but not a matched control group. Lower depression and cognitive decline rates at 2-year follow-up in the intervention group—compared with matched controls facing the same aging-related challenges—provides causal evidence that social connection improves these outcomes.

Question 21: A neuroscientist argues that sleep deprivation impairs decision-making ability. Which of the following most strengthens this argument?

Most adults require 7-9 hours of sleep per night.
In controlled experiments, the same individuals were tested on decision-making tasks after normal sleep and after 36 hours of sleep deprivation, showing significantly more risk-taking and error-prone choices in the sleep-deprived condition. (Correct answer)
Shift workers frequently experience sleep deprivation.
Decision-making is a complex cognitive process involving multiple brain regions.
Sleep quality can be measured using polysomnography.

Correct answer: In controlled experiments, the same individuals were tested on decision-making tasks after normal sleep and after 36 hours of sleep deprivation, showing significantly more risk-taking and error-prone choices in the sleep-deprived condition.

Within-subjects design (same individuals tested in both conditions) controls for individual differences in decision-making ability, directly linking sleep deprivation to performance decrements.

Answer B uses a within-subjects design—the strongest approach when feasible—testing identical individuals in both conditions. This eliminates individual differences in baseline decision-making ability as a confound. The direct comparison of the same person's performance with and without sleep provides clean causal evidence that sleep deprivation itself causes the impairment.

Question 22: An economist argues that universal pre-kindergarten education produces long-term economic benefits that exceed program costs. Which of the following most strengthens this argument?

Early childhood education focuses on social and cognitive development.
Longitudinal studies following children from disadvantaged backgrounds who attended high-quality pre-K programs showed significantly higher earnings, lower crime rates, and lower welfare dependency 30 years later compared to matched peers who did not attend. (Correct answer)
Pre-K programs require qualified teachers with specialized training.
Educational spending per student varies widely across districts.
Child development experts support early learning interventions.

Correct answer: Longitudinal studies following children from disadvantaged backgrounds who attended high-quality pre-K programs showed significantly higher earnings, lower crime rates, and lower welfare dependency 30 years later compared to matched peers who did not attend.

Thirty-year longitudinal data with matched controls directly measuring economic outcomes provides the most relevant evidence for a long-term cost-benefit claim about pre-K education.

Answer B provides the specific type of evidence that directly addresses the economic benefits claim: long-term outcome data (earnings, crime, welfare) 30 years later with matched comparison groups. This longitudinal approach captures the cumulative life-course benefits that would generate economic returns exceeding program costs.

Question 23: A physicist argues that a specific insulation material reduces heat loss in buildings more effectively than the currently used material. Which of the following most strengthens this argument?

The new material is manufactured using a proprietary process.
Side-by-side testing of identical building panels with the two materials under the same temperature differential conditions showed that the new material reduced heat transfer by 40% more than the existing material. (Correct answer)
Energy costs for building heating have risen substantially.
The material has been patented and is in commercial production.
Building energy codes require minimum insulation standards.

Correct answer: Side-by-side testing of identical building panels with the two materials under the same temperature differential conditions showed that the new material reduced heat transfer by 40% more than the existing material.

Controlled side-by-side testing under identical conditions directly measures comparative heat transfer performance, providing empirical evidence for the superiority claim.

Answer B describes the ideal comparative test: identical conditions (same temperature differential, same panel configuration) with only the material varying. The 40% measured reduction in heat transfer is a direct quantitative comparison that controls for environmental variables, providing strong empirical support for the superiority claim.

Question 24: A public policy researcher argues that needle exchange programs reduce HIV transmission among intravenous drug users. Which of the following most strengthens this argument?

Needle exchange programs provide clean syringes to drug users.
Cities that established needle exchange programs showed declining HIV infection rates among injection drug users, while cities that did not establish such programs showed no comparable decline during the same period. (Correct answer)
HIV is a serious disease requiring lifelong treatment.
Some communities have moral objections to needle exchange programs.
Intravenous drug use is associated with other health complications.

Correct answer: Cities that established needle exchange programs showed declining HIV infection rates among injection drug users, while cities that did not establish such programs showed no comparable decline during the same period.

The comparison between cities with and without programs during the same time period provides quasi-experimental evidence that the programs—not other temporal factors—caused HIV rate reductions.

Answer B provides a natural experiment: cities with needle exchange programs versus similar cities without them, during the same time period. If cities with programs showed declining HIV rates while those without programs did not, the program is the most plausible explanation for the differential trend, strongly supporting the effectiveness claim.

Question 25: A nutritional epidemiologist argues that consuming red meat more than four times weekly significantly increases colorectal cancer risk. Which of the following most strengthens this argument?

Red meat contains higher levels of saturated fat than poultry or fish.
A prospective cohort study following 500,000 individuals for 15 years found that those who consumed red meat more than four times weekly had a 35% higher rate of colorectal cancer even after controlling for age, smoking, alcohol consumption, and physical activity. (Correct answer)
Colorectal cancer is one of the most common cancer types worldwide.
Dietary guidelines in many countries recommend limiting red meat.
Some studies have found inconsistent associations between red meat and cancer.

Correct answer: A prospective cohort study following 500,000 individuals for 15 years found that those who consumed red meat more than four times weekly had a 35% higher rate of colorectal cancer even after controlling for age, smoking, alcohol consumption, and physical activity.

A large prospective cohort study with extensive covariate control and 15-year follow-up provides the strongest observational evidence available, directly addressing confounders and establishing temporal precedence.

Answer B describes a prospective cohort study—the strongest feasible design for dietary cancer research (randomized trials are not ethical or practical). The large sample size, 15-year follow-up (establishing temporal precedence), and extensive covariate adjustment (age, smoking, alcohol, activity) address major alternative explanations, providing strong support for the association.

Question 26: An educational psychologist argues that growth mindset interventions improve academic achievement in adolescents. Which of the following most strengthens this argument?

Growth mindset theory was developed by Carol Dweck at Stanford.
In a randomized trial across 65 schools, students who received a growth mindset intervention showed significantly higher GPA improvement over 6 months compared to students who received a control program, with the largest effects in students with the most room to improve. (Correct answer)
Academic achievement is influenced by many factors including teacher quality.
Some students resist psychological interventions.
Mindset can be influenced by messaging from parents and teachers.

Correct answer: In a randomized trial across 65 schools, students who received a growth mindset intervention showed significantly higher GPA improvement over 6 months compared to students who received a control program, with the largest effects in students with the most room to improve.

A large randomized trial across multiple schools with a control condition and relevant subgroup analysis directly tests the causal effect of the intervention under rigorous conditions.

Answer B describes a large, multi-site randomized trial—the gold standard for intervention research. The 65-school sample reduces concerns about site-specific factors; the randomization to growth mindset versus control program eliminates selection bias; and the subgroup finding (larger effects where there is room to improve) provides mechanistically plausible detail that strengthens the causal interpretation.

Question 27: A forensic scientist argues that DNA evidence found at a crime scene links the suspect to the location of the crime. Which of the following most strengthens this argument?

DNA analysis techniques have become highly sophisticated.
The DNA found at the crime scene matches the suspect's DNA with a probability of 1 in 10 trillion of a random match, and the sample was collected and processed using rigorous chain-of-custody procedures. (Correct answer)
DNA is found in many biological materials including hair and skin cells.
The suspect had no alibi for the time of the crime.
Criminal DNA databases have expanded significantly in recent years.

Correct answer: The DNA found at the crime scene matches the suspect's DNA with a probability of 1 in 10 trillion of a random match, and the sample was collected and processed using rigorous chain-of-custody procedures.

An extremely low random match probability combined with established chain-of-custody protocols simultaneously strengthens the evidential value and eliminates contamination as an alternative explanation.

Answer B addresses two dimensions of DNA evidence quality: (1) the 1 in 10 trillion match probability makes coincidental match virtually impossible; (2) rigorous chain-of-custody procedures rule out contamination and evidence tampering. Both are necessary for strong forensic identification evidence, and B provides both.

Question 28: An urban economist argues that increasing housing density in city centers reduces housing costs by expanding supply. Which of the following most strengthens this argument?

Dense urban housing requires different construction techniques.
Cities that upzoned and allowed high-density residential construction showed declining or stable rents in the years following increased construction, while comparable cities that maintained strict height limits saw continued rent increases. (Correct answer)
Housing affordability is a pressing concern in many major cities.
Higher density can strain existing infrastructure.
Developers prefer to build luxury units with higher profit margins.

Correct answer: Cities that upzoned and allowed high-density residential construction showed declining or stable rents in the years following increased construction, while comparable cities that maintained strict height limits saw continued rent increases.

Comparison between cities that increased density versus those that maintained restrictions during the same period provides quasi-experimental evidence linking supply expansion to rent stabilization.

Answer B provides a natural policy experiment: cities that actively increased housing supply (through upzoning) are compared with similar cities that restricted supply. Diverging rent trajectories—stable or declining where supply expanded, increasing where supply was restricted—strongly support the supply-cost relationship under real-world conditions.

Question 29: A sports scientist argues that plyometric training improves vertical jump height in basketball players more effectively than traditional weight training. Which of the following most strengthens this argument?

Plyometric training uses explosive jump and landing movements.
In a controlled 12-week study, basketball players randomly assigned to plyometric training improved their vertical jump by an average of 6 cm more than players assigned to identical-duration traditional weight training programs. (Correct answer)
Vertical jump is an important performance metric in basketball.
Some coaches prefer to combine plyometric and weight training.
Training methods should be individualized based on player needs.

Correct answer: In a controlled 12-week study, basketball players randomly assigned to plyometric training improved their vertical jump by an average of 6 cm more than players assigned to identical-duration traditional weight training programs.

A randomized 12-week controlled study directly comparing the two training methods on the specific outcome measure provides the strongest evidence for comparative superiority.

Answer B describes the ideal experimental design: random assignment eliminates selection bias (better jumpers being placed in one condition), identical duration controls for training volume, and the vertical jump outcome is the specific measure claimed to be superior. The 6 cm average advantage directly quantifies the benefit claimed.

Question 30: A toxicologist argues that exposure to a specific industrial chemical at concentrations found near manufacturing plants increases cancer risk in nearby residents. Which of the following most strengthens this argument?

The chemical is used in the production of plastics and rubber.
Animal studies exposing subjects to the chemical at these concentrations show significantly elevated cancer rates, and epidemiological data on human populations near plants shows a 2.5-fold cancer rate increase that persists after controlling for smoking and occupational exposures. (Correct answer)
Environmental regulations limit permissible chemical concentrations.
Cancer has many known and suspected causes.
Residents near industrial plants often have lower incomes and less access to healthcare.

Correct answer: Animal studies exposing subjects to the chemical at these concentrations show significantly elevated cancer rates, and epidemiological data on human populations near plants shows a 2.5-fold cancer rate increase that persists after controlling for smoking and occupational exposures.

Convergent evidence from both animal studies (establishing mechanism) and human epidemiology (with confound control) provides multi-level support that strengthens the causal cancer risk claim.

Answer B provides two independent lines of evidence: animal studies establish biological plausibility of carcinogenicity at the relevant concentrations; human epidemiological data with confound control (smoking, occupation) shows elevated cancer rates in exposed populations. Convergence of mechanistic animal data and controlled human evidence provides much stronger support than either alone.

Question 31: A political scientist argues that mandatory voting laws increase democratic representation by giving voice to typically underrepresented groups. Which of the following most strengthens this argument?

Mandatory voting exists in approximately 30 countries worldwide.
Countries that adopted mandatory voting showed that turnout increases were concentrated among lower-income, younger, and minority voters, and policy outcomes subsequently shifted toward programs benefiting these groups. (Correct answer)
Compulsory voting may conflict with freedom of political expression.
Voter registration procedures vary widely across countries.
Some mandatory voting countries have significant non-compliance rates.

Correct answer: Countries that adopted mandatory voting showed that turnout increases were concentrated among lower-income, younger, and minority voters, and policy outcomes subsequently shifted toward programs benefiting these groups.

Evidence that turnout increases are specifically concentrated in underrepresented groups, combined with policy changes benefiting those groups, directly supports both the representation and the democratic outcomes claimed.

Answer B provides two-stage causal evidence: first, mandatory voting specifically increases turnout among underrepresented groups (not just uniform increases); second, policy outcomes shift toward those groups' interests. This chain—mandatory voting → targeted turnout increase → policy representation—directly validates the representation mechanism the political scientist claims.

Question 32: A materials engineer argues that a new building material withstands earthquake forces better than conventional concrete because of its flexible molecular structure. Which of the following most strengthens this argument?

The material was developed through a 10-year research program.
Laboratory seismic simulation tests subjected identical structural components made of both materials to standardized earthquake force profiles, and the new material showed 60% less structural deformation and zero fracturing at force levels that caused significant cracking in conventional concrete samples. (Correct answer)
Earthquake-resistant construction is required by building codes in seismic zones.
The cost of the new material is comparable to conventional concrete.
Several buildings using the material are currently under construction.

Correct answer: Laboratory seismic simulation tests subjected identical structural components made of both materials to standardized earthquake force profiles, and the new material showed 60% less structural deformation and zero fracturing at force levels that caused significant cracking in conventional concrete samples.

Standardized laboratory seismic testing under identical conditions with a direct comparison provides empirical evidence of superior performance at a specific, quantified level.

Answer B describes a controlled comparative test: identical structural components, identical force profiles, different materials. The 60% less deformation and zero fracturing versus significant cracking in concrete provides quantified, direct performance comparison under relevant conditions, providing strong engineering evidence for the superiority claim.

Question 33: A conservation biologist argues that wildlife corridors connecting fragmented habitats improve species survival rates. Which of the following most strengthens this argument?

Habitat fragmentation is a leading cause of biodiversity loss.
Species in fragmented habitats connected by wildlife corridors showed significantly higher genetic diversity and lower local extinction rates over a 20-year monitoring period compared to equivalent species in unconnected isolated habitats. (Correct answer)
Corridors require coordination between landowners and government agencies.
Some invasive species can also use corridors to spread.
Land acquisition for corridors is expensive.

Correct answer: Species in fragmented habitats connected by wildlife corridors showed significantly higher genetic diversity and lower local extinction rates over a 20-year monitoring period compared to equivalent species in unconnected isolated habitats.

Long-term monitoring comparing connected versus isolated habitats on the specific outcomes (genetic diversity and extinction rates) provides direct evidence for corridor effectiveness.

Answer B provides a longitudinal natural experiment: species in corridor-connected fragments are compared with equivalent species in isolated fragments over 20 years. The combination of higher genetic diversity (indicating gene flow through corridors) and lower extinction rates (the ultimate survival measure) provides multi-metric evidence directly supporting the wildlife corridor effectiveness claim.

LSAT Logical Reasoning: Strengthen and Support Questions

A scientist argues that a newly discovered bacterium causes a specific skin disease because patients with the disease all test positive for the bacterium.
Which of the following, if true, most strengthens this argument?

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