CAT Critical Reasoning Practice question with Solution 30

QUESTION
Learning how to build a nest plays an important part in the breeding success of birds. For example, Dr. Snow has recorded the success of a number of blackbirds in several successive years. He finds that birds nesting for the first time are less successful in breeding than are older birds, and also less successful than they themselves are a year later. This cannot be a mere matter of size and strength, since blackbirds, like the great majority of birds, are fully grown when they leave the nest. It is difficult to avoid the conclusion that they benefit by their nesting experience.

Which one of the following, if true, would most weaken the argument?

OPTIONS
[A]. Blackbirds build better nests than other birds.
[B]. The capacity of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction.
[C]. The breeding success of birds nesting for the second time is greater than that of birds nesting for the first time.
[D]. Smaller and weaker blackbirds breed just as successfully as bigger and stronger blackbirds.
[E]. Up to 25 percent of all birds are killed by predators before they start to nest

Answer: B
Explanation:

Is nesting experience important for the breeding success of birds? The author uses the research of Dr. Snow to suggest that nesting experience itself must play a role in the increased breeding success of blackbirds. First-timers may not be as successful at breeding as older birds, but is nesting experience itself the only possible explanation for the difference? If another attribute related to reproduction, such as the ability to lay viable eggs (as in (B)), improved with successive nesting experience, then the author’s account of the difference becomes much less convincing.

(A) contains an irrelevant comparison. The issue is whether blackbirds benefit from nesting experience, and not whether they are better or worse than other birds at nest-building.

(C) extends the scope from blackbirds to birds in general. Still, this information would strengthen the argument by bolstering the connection between breeding success and nesting experience, which indeed is the crux of the conclusion in the last sentence.

(D) supports the author’s evidence in the next-to-last sentence, and may even therefore slightly support the author’s claim that something else besides size is responsible for blackbird breeding success. Whatever small strengthening effect (D) has, it certainly doesn’t weaken the argument at all.

(E) is irrelevant, since the percentage of birds that survive long enough to nest is unconnected to the issue of what factors influence the breeding success of those birds that do nest and reproduce.

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CAT Critical Reasoning Practice question with Solution 30

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