Zoologists have determined that the size of the litters produced by ma

Kaplan official Ansswer:
Step 1: Identify the Question Type

The question asks for additional piece of information that would "provide... support for the theory" provided. That makes this a Strengthen question.

Step 2: Untangle the Stimulus

The theory's conclusion, as repeated in the question stem, is that parent sloths choose their diet based on climate conditions in order to maintain optimal population levels. For example, when it's dry, they don't want too many offspring because there's not enough food. The evidence is that their diet effects the number of offspring. Sloths that feed primarily on catalpa trees tend to produce smaller numbers of offspring than do those that feed primarily on tulip trees.

Step 3: Predict the Answer

There's a lot to keep track of here, but consider what's unwarranted by the conclusion. The evidence merely shows how certain diets affect the number of offspring. The conclusion claims that sloths actively choose to restrict offspring through changes in diet. The author assumes there's no other reason for their dietary habits. To support this, the correct answer needs to validate that the sloths are making a conscious decision to alter their number of offspring.

Step 4: Evaluate the Choices

(D) provides support. In dry years, the sloths have equal opportunity to eat anything, but they are choosing the catalpa leaves -- the very leaves that limit the number of offspring. This does not prove the theory, but definitely makes it more likely.

(A) is a 180. Feeding on tulip leaves would lead to more offspring, the opposite of sloths would want in the dry season.

(B) is consistent with the theory -- eating tulip leaves in the wet years -- but (B) says the forest is dominated by tulip trees. In that case, it seems less like a conscious choice to affect offspring and more of "eat-what-you-see" decision.

(C) provides no information about the sloths' diets, so it provides no support for the theory in question.

(E) is a 180, as feeding on tulip leaves would lead to more offspring -- the opposite of sloths would want in the dry season.

TAKEAWAY: When a theory is presented, Strengthen the theory by finding any evidence that confirms the hypothesis.

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