Let me give this a shot. The answer is C because the conclusion states that the history book author MUST have used MORE THAN ONE source, therefore, the assumption is that if there was more than one source, that one source did not make all the same mistakes. Seeing as the book had several inconsisten...

I am a little confused by answer choice (E). I know it's not the right answer, but I was wondering if anyone knew what it meant. I guess now that I look at it again, an irrelevant consideration is not in the stimulus, but need some clarification. I can see now why the answer is really (D).

Ahh...didn't think the stimulus was confusing, but I would like to know why (C) is not the answer. Is it because it starts with "most"? I guess if something else was the cause of both snoring and smoking then that would ruin the argument. But would still like some clarification.