PrepTest 130, Section 4, Question 23
Eight large craters run in a long straight(77 more words not shown)
Which one of the following(8 more words not shown)
- AA similar but(19 more words not shown)
- BNo known natural(15 more words not shown)
- CThere is no(16 more words not shown)
- DThere is no(22 more words not shown)
- ENo known single(13 more words not shown)
Reading the argument
Eight craters in a straight line look as though they might have related origins. The shocked rocks do not settle which origin, though: both meteorite impacts and extreme volcanic events could produce those shocks.
One possibility to consider is volcanic activity along a fault line. Another is a large incoming rock breaking into pieces that land along a line. But then we learn that the craters are different ages. That creates a problem for the single-breakup idea, which would involve impacts from the same event.
The author also says a mixture of volcanic and meteorite origins is very unlikely. Given that setup, the volcanic explanation seems plausible, but I still want a clearer reason the combination of a straight line and different ages favors it. We should not treat an appealing story as established just because we can imagine it.
What we’re looking for
The strengthen question could go in either of two directions. It could offer evidence that volcanic events produce this pattern, or it could make meteorites a less plausible explanation. The useful answer will bear on the particular pattern we have, including the different ages.
Working the answers
- A
This gives some support to the possibility that volcanoes can produce a line of craters. But the example is a shorter line whose craters are all the same age. Our craters are different ages, and that feature is central to the author's choice between explanations. A provides a limited analogy without directly addressing why meteorites are unlikely to produce our pattern.
- BCorrect
This targets the meteorite explanation for the exact arrangement: eight craters, different ages, in a straight line. If no known natural cause would likely account for that meteorite pattern, the meteorite explanation becomes less plausible, strengthening the proposed volcanic explanation.
Notice that B expressly concerns meteorite craters. It is not saying that no natural cause, including volcanoes, could produce any line of craters. Also, “no known” cause that would “likely” account for the pattern does not make meteorites impossible. We need stronger support for the probable explanation, not a conclusive elimination of every alternative.
- C
A lack of independent evidence for either proposed cause does not favor volcanoes over meteorites. It also does not prove that neither event occurred. The craters and their rocks remain the evidence under discussion; C adds no reason to prefer the author's explanation of them.
- D
This supplies no additional support for a volcanic cause. If we lack independent evidence of a volcanic event powerful enough to create the shocks, that leaves the volcanic account with an unresolved evidentiary gap. It does not prove that such an event was impossible, but it certainly does not strengthen the conclusion in the requested direction.
- E
A single meteor shower concerns one event. These craters have different ages. The relevant question is whether meteorite impacts occurring at different times could produce the observed line, not whether one known shower produced exactly eight aligned craters. B addresses that different-age pattern; E does not.
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