Logical reasoning PrepTest 157 · Section 2 · Question 20

This matches our anticipation! Experienced (or time-pressed) test-takers might select this one simply because it matches their anticipation. Still, we'll run this one through our usual analysis.

When we see "fails to address" on an Errors in Reasoning answer choice, the question we should ask ourselves is, "Would this weaken the author's argument if true?"

If most mammals with short olecranon processes were not predators, that would certainly weaken this author's argument. In fact, all else being equal, that would make it more likely that the Megatherium was not a predator. At any rate, we wouldn't be able to convincingly argue that the Megatherium was a predator based solely on its short olecranon process. So, this fact would undermine the author's argument if it were true. Therefore, this is a flaw in the author's reasoning. We can pick (A) and give the remaining answer choices an, at most, quick review.

When we see "takes for granted" on an Errors in Reasoning answer choice, the question we should ask ourselves is, "Does the author believe this, and would this strengthen the argument?"

In this case, the author doesn't necessarily believe that the only reason predators need to move their front legs quickly is to attack prey. Although the author says this is one reason predators need to move their front legs quickly, the author doesn't say or imply that this is the sole reason. This is enough reason to eliminate (B).

And this wouldn't really strengthen the author's argument if true, either. This could be the only reason predators need to move their front legs quickly, but non-predators could have other reasons they need to move their front legs quickly (such as evading predators). Therefore, even if (B) were true, non-predators could benefit from short olecranon processes, making it possible that Megatherium was not a predator. This provides another reason to cross off (B). (Compare this to a different version of (B), which says, "It takes for granted that the only reason mammals need to move their forelimbs quickly is to attack prey." While the author doesn't necessarily believe this, this would at least strengthen the argument if true.)

When we see "overlooks the possibility" on an Errors in Reasoning answer choice, the question we should ask ourselves is, "Would this weaken the author's argument if true?"

This definitely wouldn't weaken the author's argument. Even if the Megatherium was a successful predator without a short olecranon process, it would still be a predator. That would support the author's conclusion that the Megatherium was probably a predator.

When we see "takes for granted" on an Errors in Reasoning answer choice, the question we should ask ourselves is, "Does the author believe this, and would this strengthen the argument?"

In this case, it's easy to assume that the author believes that the olecron processes were not generally shorter for extinct mammals. After all, the author bases the conclusion on the fact that the Megatherium had a "short olecranon process." If extinct mammals generally had shorter olecranon processes, the Megatherium could have had an average olecranon process for its era. However, the author doesn't make any statements about "extinct mammals" generally. So, it's a stretch to say the author definitely believes that the olecranon processes of extinct mammals were no shorter than living mammals'.

Moreover, (D) wouldn't weaken the author's argument if true. Even if extinct mammals generally had shorter olecranon processes, it would still be true that "the shorter the olecranon process, the faster the forelimbs can typically be moved." So, extinct mammals would generally be able to move their forelimbs very fast. This would help a mammal like the Megatherium attack prey, which would still support the conclusion that the Megatherium was probably a predator.

When we see "fails to address" on an Errors in Reasoning answer choice, the question we should ask ourselves is, "Would this weaken the author's argument if true?"

This definitely wouldn't weaken the author's argument. A longer olecranon process could provide some advantages, but those advantages would not necessarily outweigh the advantages of a shorter olecranon process for a predatory mammal. Therefore, the Megatherium's short olecranon process could still provide evidence that the Megatherium was probably a predator.