According to a recent study, advertisements in medical journals often

I think it's C.
(A) Revenue is irrelevant
(B) Editors of these journals are often unable to evaluate the advertisements. However, this answer choice doesn't say whether doctors are able to do this or not. If they are, the argument will be weakened. Therefore (B) is incorrect.
(C) Correct. If doctors don't rely on advertisements as a source of information about new prescription drugs, they won't prescribe inappropriate drugs by seeing the advertisements. This will weaken the argument. However, this answer choice eliminates this case, thus strengthening the argument.
(D) Doesn't say anything about doctors
(E) What if the doctors only see the advertisements when they have already been reviewed by the Administration? If this is the case, the drugs that get advertised to the doctors are those that pass the review. This weakens the argument.

I eliminated C because I thought it is neither strengthening nor weakening the argument and it might be an assumption but not something that strengthens it. GMATNinja please help! :)

arnimavarshney10

Yes, it's definitely an assumption. However, making assumptions true always strengthens the argument! The whole point of an assumption is that it's something unstated that is NEEDED for the argument to work. The argument fails without it, so proving an assumption true always fills a hole in the argument. True, it's not always a very large hole, but in this case it certainly is. The whole point of the argument is that the inaccuracy of ads may affect doctor's choices, but that depends completely on whether doctors get their info from these ads. Learning this makes the argument much more soild!

Short version: All assumptions are strengthens, but not all strengthens are assumptions.
_________________

KAPLAN OFFICIAL EXPLANATION

STEP 1: IDENTIFY THE QUESTION TYPE
The phrase “most strengthened” tells you that this is a Strengthen question.

STEP 2: UNTANGLE THE STIMULUS
The researchers’ argument concludes with a prediction: doctors will prescribe inappropriate drugs to their patients. This is apparently because advertisements in medical journals often contain misleading information about certain drugs.

STEP 3: PREDICT THE ANSWER
To strengthen this argument, you want a choice that gives a reason or reasons why the prediction will come to pass. What circumstances would lead to inappropriate prescriptions? Since the inaccurate information comes from medical journals, doctors will probably be more likely to prescribe inappropriate drugs if they base their decisions on what they read in the journals.

STEP 4: EVALUATE THE CHOICES
If doctors rely on the ads in medical journals to learn about new drugs, as (C) suggests, then inaccurate information could very well lead to faulty prescriptions. So (C) is correct. (A) tells you why the journals carry the ads, but it doesn’t strengthen the idea that doctors will use them to make inappropriate prescriptions. (B) could explain why the ads are published despite the inaccurate and misleading information contained in them, but like (A), (B) does not provide a bridge to doctors’ inappropriate prescriptions. (D) makes an irrelevant comparison between the accuracy of ads and that of articles. (E), like (B), explains
_________________