PrepTest 154, Section 1, Question 9
Gecko lizards are found in any environment where(40 more words not shown)
The reasoning in the argument(5 more words not shown)
- Apresumes, without providing(13 more words not shown)
- Bpresumes, without providing(10 more words not shown)
- Cdoes not consider(13 more words not shown)
- Ddoes not mention(7 more words not shown)
- Efails to establish(18 more words not shown)
Reading the argument
Maybe it's wet but too cold for the gnats.
That's a possibility the final conclusion overlooks. First, though, follow the part that works. Wherever there is an abundant gnat population, there are geckos. We have no geckos here. So we can't have an abundant gnat population here: if we did, the promised geckos would be present.
Now the author goes from no abundant gnats to a climate that isn't wet. We know gnats need wet conditions. We don't know that wet conditions alone guarantee gnats, much less an abundant population. Imagine a wet place where the temperature prevents gnats from surviving. That would fit the rule that gnats need wetness, while showing why wetness might not be enough.
What we’re looking for
The flaw question should target that last step. The lack of geckos gives us a sound reason to reject abundant gnats. It doesn't tell us why gnats aren't abundant. We shouldn't attack the first inference just because the second one fails.
Working the answers
- A
The argument doesn't need to assume geckos survive only where gnats are abundant. Geckos might live somewhere else and eat something else. The stated rule still guarantees geckos wherever gnats are abundant, and that's enough to rule out abundant gnats in this gecko-free place. A attacks a restriction the author hasn't needed.
- BCorrect
The author treats wetness as if it guarantees abundant gnats. Only with that extra guarantee could a lack of abundant gnats rule out a wet climate. But the premise runs from gnats to the wet conditions they need, not from every wet place to abundant gnats. The hypothetical wet-but-too-cold place exposes the gap.
- C
Small populations of gnats surviving in dry climates would conflict with the given premise: gnats can survive only in wet climates. Population size doesn't remove that requirement. We should accept the premise and examine what the author infers from it. The actual problem concerns wet places that might lack abundant gnats.
- D
Other foods could help explain geckos living somewhere without abundant gnats. But the author isn't arguing from no gnats to no geckos. The absence of geckos is given. We use it to rule out a condition that would guarantee geckos, then question the further conclusion about climate. Their diet doesn't identify that final mistake.
- E
Once again, gnats in a dry climate conflict with the stated premise, even if there are only a few. And whether some geckos could live in that imagined situation doesn't address the inference about this place's climate. We need to ask whether a wet place can lack abundant gnats, not create a dry place with gnats.
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