PrepTest 157, Section 2, Question 20
The olecranon process is a bony part of(57 more words not shown)
The argument is most vulnerable(9 more words not shown)
- AIt fails to(14 more words not shown)
- BIt takes for(16 more words not shown)
- CIt overlooks the(19 more words not shown)
- DIt takes for(19 more words not shown)
- EIt fails to(17 more words not shown)
Reading the argument
Predators tend to have this bone feature. Does that mean animals with the feature tend to be predators?
Those are different questions. The passage gives us a reason a short olecranon process would help a predator: it allows quicker forelimb movement when attacking prey. But perhaps other animals benefit from quick forelimbs too. Imagine that many nonpredatory animals in a jungle also have short olecranon processes for some other reason. Then finding the feature wouldn't do much to identify an animal as a predator.
What we’re looking for
That's a possibility, not a claim about actual jungle animals. It shows what we still need to know: how common the feature is among nonpredators compared with predators. The conclusion says Megatherium was probably a predator, so the objection should challenge that probability. We don't have to insist that the bone feature tells us nothing whatsoever. We need to show why information about predators alone doesn't establish the likely identity of an animal with the feature.
Working the answers
- ACorrect
Most mammals with short olecranon processes might have been nonpredators. The premise could still be true: predators generally have the feature. But if the feature also appears in a much larger group of nonpredators, finding it in Megatherium wouldn't justify treating predation as the probable explanation. A identifies exactly the missing information about the group we're using to classify the animal.
- B
Predators could move their forelimbs quickly for other purposes as well as attacking prey. That doesn't challenge the given reason that attacking prey calls for speed, and the argument never says hunting is the only reason speed matters. Our concern is whether nonpredators could also have the short bone feature, not whether predators use their forelimbs for more than one task.
- C
Maybe Megatherium could have hunted successfully without a short olecranon process. The argument doesn't need to rule that out. It reasons from the short process Megatherium actually had to its probable status as a predator. A hypothetical route to predation without that feature doesn't address whether having the feature is good evidence of predation. The premise's “generally” also allows exceptions.
- D
No comparison of average bone lengths in extinct and living mammals is needed for the stated reasoning. The relevant question is what a short process indicates about predatory behavior. D introduces a different comparison without showing that the argument relies on it.
- E
A longer process might offer greater strength or another advantage. That doesn't tell us whether mammals with shorter processes were usually predators. We aren't choosing which elbow structure is better overall. We're testing whether this particular feature supports the proposed classification.
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