Logical reasoning PrepTest 106 · Section 3 · Question 13

Question prompt

A recent study concludes Remaining source text redacted.
Why the credited answer is right

Credited answer: E

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

Strengthen Questions

Stimulus Summary

Question - Did modern warm-blooded birds descend from birds that were warm- or cold-blooded?
View 1 - Cold-blooded, because prehistoric birds had growth rings that are believed to be exclusive to cold-blooded animals.
View 2 - Warm-blooded, because prehistoric birds had dense blood vessels in their bones, meaning they were active/warm-blooded.

Answer Anticipation

First, let’s talk about the question type here. The stem tells us that there are multiple parties, and we’re looking for an answer that presents information allowing us to determine which is right and which is wrong. From this, we can tell a couple things. We know that there are two viewpoints that can’t both be correct, and we know that we’re looking for an answer that tells us which is right. For lack of a better question type, we’re going to call this an Argument Evaluation question. However, instead of an answer that would help determine whether the argument is valid or invalid, we’re looking for an answer that will strengthen one argument and weaken another.
So with that noted, let’s dig in. The argument starts with information from a recent study that “challenges” a widely held view, suggesting the debate at the heart of this question - did modern (warm-blooded) birds descend from cold- or warm-blooded birds? Since those are the only two possibilities, evidence for one is evidence against the other, and evidence against one is evidence for the other.
The cold-blooded side brings up growth rings to support their view, noting that growth rings are “thought to be found only in” cold-blooded animals. However, that leaves open the possibility they are also found in warm-blooded animals, we just haven’t discovered that yet. Any answer that deals with the connection between growth rings and warm/cold-bloodedness will help determine which of the two sides of the debate is correct!
The same can be said for the evidence for the warm-blooded side. They rely on the dense blood vessels in the prehistoric birds to prove their point. These blood vessels are associated with a lot of activity and thus warm-bloodedness. Any answer that strengthens or weakens this evidence for the claim will serve to determine which side is correct!

Answer choices

  1. A
    Some modern warm–blooded species Remaining source text redacted.
    Why choice A is not credited
    Establishing that a warm-blooded species can descend from a cold-blooded one doesn’t do anything to support that view, as it was already a possibility established by the stimulus. If this answer connected birds and these species in some way, it might help, but it doesn’t, so it’s out of scope.
  2. B
    Having growth rings is Remaining source text redacted.
    Why choice B is not credited
    Without discussing these other traits and whether they were present in prehistoric birds, this answer doesn’t do anything to affect the argument.
  3. C
    Modern birds did not Remaining source text redacted.
    Why choice C is not credited
    Both views believe that modern birds evolved from prehistoric birds - the question is whether those birds were warm- or cold-blooded. As such, this answer undermines both views, which doesn’t address the question stem, where we’re tasked with helping resolve the dispute in favor of one part over the other.
  4. D
    Dense blood vessels are Remaining source text redacted.
    Why choice D is not credited
    Close! But we know that prehistoric birds did have dense blood vessels, and this answer doesn’t question whether all species with dense blood vessels are warm-blooded. The reversal of this answer (some animals with dense blood vessels aren’t warm-blooded) may weaken it, but this answer doesn’t.
  5. E
    In some cold–blooded species Remaining source text redacted.
    Why choice E matches the stem
    This answer establishes that there are cold-blooded species with both growth rings and dense blood vessels. As such, the dense blood vessels don’t guarantee the prehistoric birds were warm-blooded. Since the prehistoric birds being cold-blooded aligns with all information, this answer suggests that view is correct, and it is therefore correct.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A 10%
  2. B 7%
  3. C 7%
  4. D 7%
  5. E Credited 68%

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