Logical reasoning PrepTest 155 · Section 2 · Question 26

Incorrect. Since the stimulus doesn't tell us about the speed of stickleback predators, this answer choice is out of scope.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Ocean fish have armor for protection, but lake fish don't. Armor limits speed of growth. Therefore, size is more important for protection than armor in lake fish.

Strategy Overview:

Answer Anticipation:
In this argument, the author picks one explanation for a phenomenon—mainly, that the armor for size tradeoff in lake fish is because of predation. However, without ruling out other reasons that the fish don't have armor, we can't conclude it's because of predators, just because the armored ocean fish use the armor for protection from predators. Any answer that brings up an alternative for why the fish don't have armor would weaken this explanation. Bonus points if the answer explains why the ocean fish are better off with armor over size.

Answer Explanation:
This answer gives us an alternative explanation for the difference—they need the size to survive winters. It also explains why the ocean fish are difference. This is the answer.

Key Takeaway:
When an argument presents an explanation for a phenomenon, the correct answer to a Weaken question will generally provide an alternative explanation.

Incorrect. Since there's no information about how armor and size protect fish from insects, this answer choice doesn't provide enough information for us to evaluate its impact on the argument.

Incorrect. This answer choice brings up a similarity between the two fish, which, if anything, would strengthen the argument that the difference is because of the predators, since this suggests their diets don't affect the armor.

Incorrect. This answer choice doesn't give us an alternative explanation, so it's incorrect.