PT 49, S4, Q2 Eating garlic reduces the levels

[noah]

2. (B)
Question type: Assumption
While this question does not expressly ask us to identify an assumption of the argument, when considering which question would help us evaluate the argument, we’re looking for a question for which the answer could strengthen or weaken the conclusion. The firmest way to strengthen or weaken a conclusion is either to make explicit an assumption or to explicitly negate an assumption.

This argument concludes that eating garlic lowers the risk of heart problems. Garlic does this by lowering cholesterol and triglycerides. The evidence is that people taking garlic pills had much lower levels of both substances when compared to a similar group of people who took a placebo. While it may be hard to predict the specific issue that could strengthen or weaken this argument, the answer to (B) is quite relevant. If the people in the placebo group ate a lot of garlic every day, the experiment would not prove that garlic had the effect of lowering cholesterol and triglycerides.

(A) out of scope. The pills availability has no effect on their efficacy.
(C) is a very tempting answer. However, the conclusion that can be drawn from the given evidence is not that any ingestion of garlic leads to lower cholesterol and triglyceride levels. Instead, we can only draw conclusions about the effects of ingesting as much as the garlic-pill group indeed took, though such conclusions might be flawed for other reasons.
(D) out of scope. The pills could destroy your kidneys yet still be good for your heart.
(E) out of scope.

[maria487]

Can someone elaborate on why (C) is incorrect? The way I see it, if one evaluates the effect of taking the garlic tablet for less than 4 months and the same result is not yielded (beneficial effects are reduced), that weakens the conclusion, no?

[maryadkins]

But what is "less than four months?" Is it one week? Two days? Because no, I wouldn't actually consider that data useful; it's too short a time span. (C) is so vague about duration that it could, in a reasonable interpretation, be totally moot, which makes (B) a better answer.