by bbirdwell Tue Jan 15, 2013 12:28 pm
I agree that the argument never explicitly says that cigar smokers don't smoke cigarettes. But I don't think it needs to. The first sentence sets up an exclusive dichotomy that does the job well enough: cigar smokers have lower risk than cigarette smokers.
This "lower risk" label wouldn't apply to cigar smokers who also smoke cigarettes, because then they'd have to be considered cigarette smokers. See what I mean?
While you have definitely pointed out a subtle "hole" of sorts in the answer choice (it's POSSIBLE that cigar-smokers have smoked cigarettes before), notice the question stem here:
"...offers the best prospects for explanation"
So there ya have it -- the answer choice isn't expected to be an airtight explanation like it might be on a question that read "which choice resolves the paradox."
Our task here isn't to make the idea bullet-proof, it's just to take the best of five steps in that direction.
Quick breakdown:
1. pipe-smokers have lower risk than cigarette smokers
2. cigarette smokers who switch to pipe do not reduce risk
big question: why isn't risk reduced when switching from cigarettes to pipes?
(A) doesn't help us answer the question - wrong group
(B) who cares about this group? We want to know about cigarette smokers who switch to pipes.
(C) Same as B
(D) no help at all in resolving the issue of reducing risk
(E) Ah-ha! Even though they're smoking the same stuff, cig-smokers smoke in a different way! This could at least possibly (if not probably) explain it! Easily the best of the five.
Hope that helps!