Logical reasoning PrepTest 127 · Section 2 · Question 4

Incorrect. While the core areas must contain enough food for the warblers to survive (otherwise they'd all die), it's not necessary that this core area has "just" enough food. If there's some extra food, the argument can still hold as long as no animals are competing for that food.

Incorrect. The singing of warblers to mark territory could be common in the bird world and still work for warblers.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Assumption

Stimulus Summary:
Warblers signal to each other where their territory is with song. There's some overlap between feeding territory, but a molting warbler has a special song and other warblers don't intrude on its core territory. Thus, molting warblers don't have competition for food.

Answer Anticipation:
The premises all talk about how warblers warn off other warblers, but the conclusion here is much broader than that—it talks about a lack of competition overall. While other warblers won't intrude on a molting warbler's core territory, it's possible that some other animals will still look for food in that territory. This argument assumes, without establishing, that that isn't the case, so the correct answer should establish that.

Answer Explanation:
The conclusion is about competition generally, whereas the premises are all about competition between yellow warblers. That jump represents a massive assumption of the argument that nothing else is eating the yellow warbler's food. If there are other birds that compete with the warbler for food, then they may not be scared off by the warbler's warning song and thus a molting warbler might have some competition for food. Note that even though the argument assumes no animal competes with these warbler's for food, that means it's necessary to assume that no birds compete with them (the difference between a Strengthen with Sufficient Premise question and a Strengthen with Necessary Premise question). If there are birds that compete with these warblers for food, then the argument falls apart.

Key Takeaway:
Whenever a conclusion makes a relatively strong claim—here, "no competition"—you should start to analyze whether the premises back up a claim of that strength. You'll frequently find that the premises don't, and noting those Weak Premises can help you find the correct answer quickly.

Incorrect. The argument requires that other animals don't compete with the warblers for food in their core areas while they're molting. Whether that's because there are no other animals in the area or there are but they eat different things doesn't matter, so this answer, in establishing one of multiple possibilities, isn't necessary for the argument to work.

Incorrect. The size of the territory doesn't matter—just any competition that the warblers might face there.