PrepTest 111, Section 1, Question 17
On the basis of the available evidence, Antarctica(80 more words not shown)
The reasoning in the argument(10 more words not shown)
- AThat a given(21 more words not shown)
- BThat either of(27 more words not shown)
- CEstablishing that a(13 more words not shown)
- DA claim that(17 more words not shown)
- EAn inconsistency that,(17 more words not shown)
Reading the argument
Why must the melting have happened three million years ago? That is the age of the fossils, but the ice could have melted earlier. Suppose it melted five million years ago and the area remained submerged when the fossils were deposited two million years later. The fossils could still be three million years old. The author hasn't ruled out that different timeline.
I also want to know whether melting and flooding are the only ways to account for finding the fossils there. Could something have transported the material? Have we established that these organisms could occur only in the ocean, or merely that this is where their fossils had previously been found? We don't need to prove an alternative to notice that the argument hasn't eliminated alternatives.
What we’re looking for
The warming and volcanic activity give us ways the proposed melting could have happened. They don't turn that proposal into the only possible explanation. For the flaw question, my strongest initial concern is the timeline, with the possibility of another route for the fossils also in view. Look for an answer describing the jump from a possible account to something that must have happened.
Working the answers
- A
The author challenges the widely held view that Antarctica stayed covered in ice. That is the opposite of accepting a position merely because it is widely believed. Popularity provides the background view being questioned, not proof of the conclusion.
- B
This would accuse the author of ruling out a combined effect of warming and volcanic activity just because either could work alone. The author doesn't make that claim. Mentioning two possible mechanisms doesn't establish that they couldn't operate together, and the argument doesn't rely on excluding their joint operation.
- C
The author isn't arguing, “We know it melted, so we know what caused the melting.” The conclusion is that melting must have occurred about three million years ago. Warming and volcanic activity are offered as possible mechanisms, not a settled finding about its cause. C targets a different inference.
- D
The conclusion concerns a particular period in Antarctica's history. It doesn't take these fossils and make a sweeping claim about all ice sheets or every continent. Limited evidence might leave questions unanswered, but that isn't the same as using a few cases to support a very general rule.
- ECorrect
The apparent conflict is between continuous ice cover and the presence of fossils associated with ocean-floor sediments. The author resolves it through a particular melting event and treats that resolution as required.
But another timeline, or another account of how the fossils reached the site, could also address the apparent conflict. E captures the common problem behind both objections: the evidence needs an explanation, but the author hasn't shown that only this explanation can work. The wording is broader than my initial timing concern, and that broader description fits the mistake.
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