A. This is basically stated in the passage already: "neither group knew which they were receiving." At best, then, this strengthens the conclusion that the drop in symptoms was a result of the effectiveness of the drug.

B. Aha! This is unquestionably correct. Even though neither group was told which pill they received, the patients in the fluvoxamine group were able to determine that they had been given the actual drug, and not a placebo. Once they figure this out, then they might assume that they will feel better, because that is what the drug is supposed to do. Their improvement, then, cannot be attributed only to the drug, but also to the positive thinking associated with the knowledge that one has received a drug that is supposed to improve their condition.

C. The argument does not claim that all patients will improve. Actually, the conclusion reports a mild 15% greater chance of having reduced symptoms. So the drug only works for around 15% of the people, not everyone.

D. This might give a reason for not relying on fluvoxamine, but the conclusion does not say that fluvoxamine should be prescribed. It only says that fluvoxamine is responsible for the drop in depression symptoms, which can still be true even if it does cause psychosis at large dosages.

E. Again, the conclusion is only that fluvoxamine is responsible for the decrease in depression symptoms. This could be true even if some patients reacted very poorly to it.