­Scientists studying fossils of a species of dinosaur found stones in

Explanation

­Scientists studying fossils of a species of dinosaur found stones in the dinosaurs' stomach area. These dinosaurs were vegetarians, but their teeth could not have chewed a sufficient quantity of vegetation well enough to provide nutrition to support their large size. Thus, the stones may have served to help grind up the dinosaurs' food, just as happens with ostriches and some other modern birds. Alternatively the stones may have served as nutritional supplements, supplying minerals not found in vegetation in large enough quantities.

We see that the passage presents two possible purposes of the stones:

the stones may have served to help grind up the dinosaurs' food

the stones may have served as nutritional supplements, supplying minerals not found in vegetation in large enough quantities

The support for both hypotheses is the following:

These dinosaurs were vegetarians, but their teeth could not have chewed a sufficient quantity of vegetation well enough to provide nutrition to support their large size.

We see that the reasoning supporting the hypotheses is that, since the dinosaurs' teeth could not have chewed a sufficient quantity of vegetation well enough to provide nutrition to support their large size, the stones must have either helped them grind the vegetation or provided additional nutrition.

In order to help decide between the two hypotheses for the stones' function, which of the following would it be most useful to know?

The answers to the question presented by the correct answer will either weaken the case for one of the hypotheses, strengthen the case for the other, or weaken the case for one while also strengthening the case for the other.

(A) Whether the stones had sufficient volume to efficiently grind the vegetation that served as the dinosaurs food

The answers to the question presened by this choice would help with determining whether the hypothesis that the dinosaurs swallowed the stones for the purpose of grinding their food is correct. After all, if the answer to the question presented by this choice is "Yes," then it is reason to believe that the dinosaurs swallowed the stones for food grinding purposes, and if the answer to this question is "No," then it is reason to believe that the dinosaurs did not swallow the stones for food grinding purposes.

Now, the answers to the question presented by this choice have no direct effect on the case for the hypothesis that the stones may have served as nutritional supplements because, regardless of whether the stones had sufficient volume to efficiently grind the vegetation that served as the dinosaurs food, they could have served as nutritional supplements.

At the same time, if we have the answer to the question presented by this choice, then we do have at least some indication regarding whether the stones served as nutritional supplements. After all, if the stones did not have sufficient volume to efficiently grind the vegetation, then they likely served some other purpose, information making it more likely that the stones served as nutritional supplements.

So, we can see that the answers to the question presented by this choice indicate both whether the stones served to grind the vegatation and whether they served as nutritional supplements, with a Yes answer to the question supporting the vegetation grinding hypothesis over the supplements hypothesis and a No answer supporting the supplements hypothesis over the vegetation grinding hypothesis.

Keep.

(B) Whether the stones swallowed by ostriches or other modern birds serve to provide any nutritional minerals

The correct answer must present a question such that the answers indicate that the stones served ONE OR THE OTHER of the two possible purposes mentioned by the passage.

On the other hand, since we already know that stones swallowed by ostriches help to grind their food, the answer to this question would indicate whether the stones serve BOTH of the two possible purposes mentioned the passage. So, the answers would not indicate what we need them to indicate.

Eliminate.

(C) Whether stones were found in the stomachs of related species of dinosaurs

Notice that, regardless of whether stones were found in the stomachs of other species of dinosaurs, we still would not have information on WHY the stones were there, and the correct answer to this question must be one such that the answers to the question it presents indicate what the purpose of the stones was.

Eliminate.

(D) Whether any large modern animals typically eat the same sort of vegetation as did these dinosaurs

Whether any large modern animals eat the same sort of vegetation as these dinosaurs ate has no bearing on the argument. After all, the point of the argument is not whether they ate the vegetation or whether the vegatation could have provided sufficient nutrition.

The point is that the dinosaurs' teeth were such that they could not have gotten the nutrition they needed by chewing vegetation, so tbey needed to get it in some other way, and we are seeking to determine which way that was.

Now, if this choice were about modern animals using stones to grind food or getting nutrition from stones, the answers to the question it presents might indicate something about why the dinosaurs ate the stones.

As this choice is, though, the answers to the questions it presents have no effect on case for either hypothesis.

Eliminate.

(E) Whether there is any evidence of the presence of the relevant nutritional minerals in the fossilized bones of these dinosaurs­­

Notice that this choice is about "the fossilized bones" of the dinosaurs. When bones fossilize, their composition changes from what it orignaly was when the animal that had the bones was living.

So, this choice is not about whether the bones of the dinosaurs contained any minerals. It's about whether the bones still have minerals they would have contained while the dinosaurs were living.

After all, the passage says the following:

their teeth could not have chewed a sufficient quantity of vegetation well enough to provide nutrition to support their large size

We see that the passage indicates that the dinosaurs definitely needed nutrition they could not get by chewing vegatation. So, there is no question that, when they were alive, their bodies were using nutrition, such as minerals, that they would have taken in in some way other than chewing vegatation.

Thus, regardless of what the answer to the question presented by this choice is, the dinosaurs could have gotten necessary nutrition from the stones.

So, the answers to the question presented by this choice have no effect on the case for either hypothesis.

Eliminate.

Correct answer: A­