Logical reasoning PrepTest 148 · Section 1 · Question 5

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Early in life, a moth eats a plant that makes it toxic to predators. Since that plant is facing extinction, the moth is also in danger.

Answer Anticipation:
The plant is certainly offering protection against predators for the moth, but there's no indication that:

(1) Without the protection, the moth would be in danger of extinction—it might not have enough predators to do that

(2) There aren't other sources of protection for the moth

The argument requires that, without the plant, the moth will be hunted into extinction, so any answer that deals with the two aspects of that listed above should be considered.

Answer Explanation:
This answer deals with the gap in the argument—mainly, that the only thing protecting it is the toxicity it gets from eating this plant. If there are other means that the moth can use to make itself unpalatable to predators, then the extinction of this plant doesn't threaten the moth as well.

Key Takeaway:
Remember—just because something works doesn't mean it's the only thing that works. While that's normally applied to problem/solution passages, it can also be relevant in a question like this, where the problem/solution is more background than the core of the argument.

Incorrect. Tempting! This answer seems to eliminate other means of the moth protecting itself. However, it's too extreme in stating that it doesn't have speed/agility to escape from "any" of would-be predators. If it does have speed/agility to escape from one would-be predator, the remaining ones could still potentially hunt it into extinction.

Incorrect. It's unclear how this would affect their behavior. If they could tell, then they might avoid all of the moths since they have this chemical. If they couldn't, they still might avoid all the moths since they wouldn't know which ones taste bad. Since this answer has an unclear impact on the argument, we should eliminate it.

Incorrect. While this might make it more likely that they're at risk sooner rather than later, it's not necessary that they have a hard time finding the plants when they're rare since the premise is about them going extinct—in other words, impossible to find.

Incorrect. This answer is too extreme. The argument doesn't require that every predator species is intolerant of macrozamin—just enough that it protects the moth species from going extinct from overpredation.