PrepTest 113

[lcid:3551] Prep Test 113 LSAT — Logical Reasoning — S4 Logical reasoning

Question prompt

A plausible explanation of Remaining source text redacted.
Why the credited answer is right

Credited answer: B

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Argument

Valid or Flawed

Flawed

Question Type

Weaken Questions

Stimulus Summary

Comet Theory - A large comet kicked up enough dust to cool the planet and kill the dinos
Conclusion - The Comet Theory is plausible

Answer Anticipation

This stimulus brings up the details of a specific theory before drawing a judgment about it. Theories are meant to explain phenomena, and they’re generally causal, so we can rely on all of these patterns and concepts to help us answer this question.
But first let’s talk about the judgment - the Comet Theory, according to the argument, is “plausible.” This means that the argument is reasonable or believable, which isn’t the highest bar. As such, to weaken that determination, we’ll have to find an answer that does a pretty good job of ruling out the theory, since we need to essentially support the judgment that this theory isn’t plausible.
The specifics of the theory here are going to be important. The argument explains the plausibility of the theory with a causal chain - the comet collided with Earth, causing dust to be kicked up, which caused the planet to cool, which caused the dinosaurs to die. However, these relationships are all presented as possibilities - this is what “could” have happened. As such, any answer that calls any of these relationships into question will weaken the theory.

Answer choices

  1. A
    One of the various Remaining source text redacted.
    Why choice A is not credited
    There being another theory doesn’t weaken this theory! Just because some people out there believe the Earth is flat doesn’t weaken the argument of those who believe it’s round. (Which it is.)
  2. B
    Various species of animals Remaining source text redacted.
    Why choice B matches the stem
    This answer attacks a part of the potential causal chain - the statement that the cooled climate would have led to the dinosaurs’ demise. The cause brought up in the Comet Theory isn’t specific to dinosaurs - every animal on the planet would have been affected by the dust cloud and changing climate. Physiologically similar animals should have reacted to a cooling of the Earth in a similar manner to the dinosaurs. If they survived this period, then this suggests that the cause of the dinosaurs’ extinction wasn’t something that generally affected the entire planet and was more specific to them. This answer thus undermines the Comet Theory and is correct.
  3. C
    It cannot be determined Remaining source text redacted.
    Why choice C is not credited
    First, the Comet Theory brings up that it was the cooling climate and not the dust itself that killed off the dinosaurs. Second, even ignoring that, the inability to prove a theory using a specific method doesn’t weaken that theory. It’d be like saying we can’t prove the moon has a lot of dust on it by looking at it with a cell phone camera, and so it’s less likely that it has a lot of dust on it.
  4. D
    Many other animal species Remaining source text redacted.
    Why choice D is not credited
    Compare this answer to (B) in order to see why it’s incorrect and that answer is correct. This answer does establish that many animals from the same time period survived, but it doesn’t establish - as (B) does - that those animals were relevantly similar. This doesn’t just make (B) better than this answer, but it makes (B) an answer that weakens the argument and this answer an answer that doesn’t. To use an analogy to highlight it, it’d be like saying humans survive on land, and so removing fish from water and putting them on land can’t be what caused them to die.
  5. E
    The consequences for vegetation Remaining source text redacted.
    Why choice E is not credited
    Even if the consequences aren’t fully understood, they could be understood enough to know that they killed off the dinosaurs.

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