Logical ReasoningDifficulty: Medium

PT135 S2 Q19 Explanation

One theory to explain

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsWeaken

Keep going in LSAT Lab

  • Save & drill this skill — build targeted practice sets from questions like this one

  • Video walkthroughs — watch every question solved step by step

  • 81 official LSATs — as questions, timed sections & full-length tests

Start practicing free

Free to start

Full official LSAT questions are available through LawHub. This page provides LSAT Lab's explanation, strategy, and review tools without republishing the full official question.

Stimulus

One theory to explain the sudden extinction of all dinosaurs points to "drug overdoses" as the cause. Angiosperms, a certain class of plants, first appeared at the time that dinosaurs became extinct. These plants produce amino-acid-based alkaloids that are psychoactive agents. Most plant-eating mammals avoid these potentially lethal poisons because they taste that it helps explain why so many dinosaur fossils are found in unusual and contorted positions.

What this question is testing

Weaken

Your task

Find the choice that makes the argument's conclusion less likely to be true.

Common trap

Answers that look negative but attack a claim the argument never relied on.

Winning move

Find the assumption the argument depends on, then pick the choice that undermines it.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
19.

Which one of the following, if true, would most undermine the theory

Answer choices

  1. Correct75% picked this

    Many fossils of large mammals are found in

    Why this is right

    This weakens the argument by providing the same observation (fossils found in contorted positions) in a context unlikely to have the same cause—mammals avoided eating angiosperms that produced amino-acid-based alkaloids because they were bitter.

    Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

  2. Out of Scope5% picked this

    Angiosperms provide a great deal of

    Regardless of whether angiosperms provide a great deal of nutrition, the question is whether they are responsible for the extinction of all dinosaurs.

  3. Strengthens12% picked this

    Carnivorous dinosaurs mostly ate other, vegetarian, dinosaurs that fed

    This strengthens the argument by resolving a gap in the reasoning—how the carnivorous dinosaurs could have died as a result of toxic plants.

  4. Strengthens5% picked this

    Some poisonous plants do not produce amino­ acid-

    The asserted cause of the extinction of all dinosaurs is poisonous plants. This answer increases the amount and variety of poisonous plants and thereby increases the chances that the explanation is correct.

  5. Strengthens3% picked this

    Mammals sometimes die of drug overdoses from

    This supports the causal explanation by showing a similar cause and effect relationship within another context.

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill
LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free