Logical reasoning PrepTest 135 · Section 1 · Question 12

Question prompt

Populations of a shrimp Remaining source text redacted.
Why the credited answer is right

Credited answer: C

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

Argument or Facts

Facts

Valid or Flawed

NA

Question Type

Paradox Questions

Stimulus Summary

Baby shrimp are carried between reefs, allowing for genetic mixing. So it’s weird that the reefs are genetically different from each other.

Answer Anticipation

There’s a key term here that can serve as our jumping-off point in finding an explanation - “allow.” The stimulus doesn’t state that the baby shrimp being carried to other reefs results in them interbreeding - it states that it allows them to interbreed. Since the interbreeding would result in genetic mixing that would prevent the differences from developing, the baby shrimp must not actually interbreed after getting carried to the other reefs.
We’re not sure what form the correct answer will take, but it will provide an explanation for what happens after the baby shrimp get carried to the other reefs that stops them from then interbreeding with the other shrimp they find there, instead breeding with shrimp from their reef and then returning back.

Answer choices

  1. A
    The genetic differences between Remaining source text redacted.
    Why choice A is not credited
    While that may be the case, the genetic differences are still “substantial,” and if they were interbreeding as expected, they’d be genetically indistinguishable, so this answer is incorrect.
  2. B
    The individual shrimp within Remaining source text redacted.
    Why choice B is not credited
    The stimulus talks about genetic differences on a population scale, and it establishes both that these shrimp groups are genetically distinguishable, and that interbreeding ones aren’t. This answer choice, therefore, doesn’t resolve the issue.
  3. C
    Before breeding, shrimp of Remaining source text redacted.
    Why choice C matches the stem
    This answer explains how the shrimp avoid interbreeding once carried to other reefs. Instead of staying there and having their own babies, they swim back to their reefs, thus preventing the interbreeding that would result in genetic indistinguishability.
  4. D
    Most shrimp hatched at Remaining source text redacted.
    Why choice D is not credited
    If anything, this makes the paradox worse - if they’re not at the reef they were born at, then it seems as if they are staying where they were carried, or going to another reef, and thus there should be interbreeding and not persistent genetic differences between the reefs.
  5. E
    Ocean currents probably carry Remaining source text redacted.
    Why choice E is not credited
    This might explain something about population size not being as big in the reefs as birth levels would suggest, but it doesn’t explain why the baby shrimp carried elsewhere don’t interbreed in these other reefs.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A 2%
  2. B 13%
  3. C Credited 74%
  4. D 4%
  5. E 7%

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