People with a certain medical condition tend to have lower levels of

­People with a certain medical condition tend to have lower levels of low-density lipoprotein cholesterol (LDL-C) before they are diagnosed with this condition than do people without this condition. This association is equally strong whether or not the individuals have taken medications to lower their LDL-C. Therefore, having taken such medications does not make it more likely that people with lower LDL-C will develop the condition in question.

The conclusion of the argument is the following:

having taken such medications does not make it more likely that people with lower LDL-C will develop the condition in question

The reasoning of the argument is basically that, since the association between having low LDL-C and being diagnosed with the condition is the same regardless of whether people have taken medications to lower LDL-C, the medications don't help to cause people to develop the condition.

The doctor’s argument is most vulnerable to criticism on which of the following grounds?

This question is a Logical Flaw question, and the correct answer will describe an aspect of the argument that's a flaw.

A. It presumes that if a medication to lower LDL-C does not strengthen the association between lower LDL-C and a medical condition, the medication does not help cause the condition.

The choice perfectly describes a flaw in the argument.

After all, the argument uses one premise, that the association betwen LDL-C and the condition is the same regardless whether the person experiencing the condition used medications, to support the conclusion that medications do not help to cause the condition.

That the argument does so is a flaw because, even if medications don't affect that particular assoication, they could still cause the condition. After all, they could cause the condition without affecting that association. So, the fact that medications don't change that association doesn't necessarily mean that they don't help to cause the condtion.

Thus, we could say that, in presuming that if medications do not strengthen the association, they don't help to cause the condition, the argument makes an unwarranted assumption.

Keep.

B. It confuses a claim about a medication’s effects with a claim about the effects of a condition the medication is intended to treat.

This choice is incorrect because the argument simply doesn't do what this choice says.

After all, the argument doesn't mention the effects of the condition and doesn't confuse the effects of medications with the effects of the condition. Rather, it keeps clear the effects of medications, which are to lower LDL-C and, possibly, to help cause the disease.

Eliminate.

C. It takes for granted that a factor that is not known to cause a given effect cannot cause another effect associated with the first.

Let's break this choice down to see why its incorrect:

a factor that is not known to cause a given effect

The only factor that the passage mentions as not being known to cause an effect is "taking medications," which the passage claims "does not make it more likely that people with lower LDL-C will develop the condition in question."

On the other hand, "taking medications" to lower LDL-C would obviously be known to cause "low levels" of LDL-C.

another effect associated with the first

The only two "associated" effects mentioned in the passage are the "condition" and "low levels" of LDL-C., and "the first" would be the one that "taking medications" is not known to cause, meaning "another effect" must be "low levels" of LDL-C.

So, let's now translate this choice to make it specifically about this passage.

It takes for granted that a factor (taking medications) that is not known to cause a given effect (the condition) cannot cause another effect (low levels of LDL-C)  associated with the first (the condition).

Having translated the choice, we see that it basically says that the argument takes for granted that "taking medications" does not cause "low levels" of LDL-C.

Since, clearly, the passage does not say or imply that taking LDL-C lowering medications does not cause low levels of LDL-C, this choice is incorrect.

Eliminate.

D. It overlooks the possibility that even if one factor does not cause another, they may be strongly associated.

It's true that the argument does not address the possibility that, even if medications do not cause the condition, medications and the condition may be associated.

At the same time, the fact that the argument does not address that possibility is not a flaw in the argument. After all, as long as medications do not cause the condition, the conclusion is correct, regardless of whether medications and the condition are strongly associated.

Eliminate.

E. It takes for granted that if two factors are associated with each other whenever a third factor is absent, the association can also hold even when that third factor is shown to be present.

This choice is incorrect because the argument doesn't take for granted, i.e., assume, that the association between low LDL-C and the condition holds when medications are present. Rather, it states as fact that "this association is equally strong whether or not the individuals have taken medications to lower their LDL-C."

Something the argument states as fact is not something the argument takes for granted, or assumes.

Eliminate.

Correct answer: A­