Logical reasoning PrepTest 114 · Section 4 · Question 23

Incorrect. First, the stimulus discusses only one such anatomical characteristic, not many. Second, it doesn't establish that it was a disadvantage to the Acanthostega or any predecessor that shared that feature.

Incorrect. The argument at most discusses a single anatomical characteristic common to most aquatic animals (gills), so this answer that speaks about all of them is too broad.

Incorrect. While this might be possible, there's no indication that it's definite, so we can eliminate this answer.

Incorrect. The anatomical characteristic common to most land animals in the stimulus (rotating limbs terminating in digits) is useful for land movement. So, there's no example of a characteristic described in this answer in the stimulus, let alone a strong enough statement to support something as true about all such characteristics.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Most land-dwelling vertebrates have rotating limbs and digits (useful for land movement)
Acanthostega - Ancestor of land vertebrates; has rotating limbs and digits; is exclusively aquatic

Answer Anticipation:
This is one of those Must Be True questions where it'll be nearly impossible for us to get a good idea of what the correct answer is ahead of reading it! There are no real statements that build together to form an inference.

What we are given is a comparison between most land-dwelling vertebrates and the Acanthostega. Both have rotating limbs and digits, but the Acanthostega was exclusively aquatic, whereas land-dwelling vertebrates, well, live on land.

These two points of comparison will likely factor into the correct answer choice, but it's unclear how they will do so, so let's head into the answer with them in mind while staying flexible.

Answer Explanation:
This answer is super weak ("certain", "some"), so it is easy to support. Since there's an example in the stimulus of a characteristic (rotating limbs terminating in digits) common to some aquatic animals (Acanthostega) that is an advantage for survival on land, this answer is strongly supported and thus correct.

Key Takeaway:
When an argument provides a single example and you're about to pick an answer that generalizes from it, be sure that the answer is a weak generalization. It should talk about what sometimes or can or might happen, or what is possible. If it's stronger than that, a single example just won't cut it!