Take the driver's argument in question 21 of Section 2 of the June 2007 LSAT with a giant grain of salt. Imagine you're this guy's friend--you're one of the friends that has been telling him he's going to die someday because he drives like an A-hole. He tells you, in response, that he's going to lower his risk of having an accident by switching to a minivan, which has a lower accident rate. What are you going to tell him? STOP. DO NOT LOOK AT THE ANSWER CHOICES! The answer is more easily found by criticizing the argument, rather than by sorting through the answer choices. Argue with the driver. He says a minivan will protect him. What are you going to say?
I'm going to say "minivans have lower accident rates because they're usually driven by Soccer Moms and other folks who drive safely. You, my soon-to-be-former friend, drive like an A-hole. Switching to a minivan is unlikely to stop you from driving like an A-hole. If you blast your new minivan around town like you're driving the A-Team van, I don't think the magical safety powers of the minivan are going to accrue to you. (Hell, the way you drive, you could make this thing dangerous.)
Catch my drift? The driver has assumed that just because minivans are correlated with lower accident rates, that minivans must cause lower accident rates. That's a logical no-no. Correlation does not prove causation.
The question says "The reasoning in the driver's argument is most vulnerable to criticism on the grounds that this argument..." In other words, why is the argument bullshit? What's the flaw? I think the flaw has something to do with the correlation-causation problem I've already identified. NOW it's time to go on to the answer choices.
A) Yep. This is exactly what I was looking for.
B) This is sometimes the correct answer, but it can only be the correct answer if the facts that were presented give us a solid reason to believe that the sample was too small or unrepresentative. We were given no such clues. No way.
C) This would be the answer if the argument had said "minivans have less accidents, so I definitely won't have any accidents in a minivan." That's not quite what the argument did, though.
D) This would be the answer if the argument had said "B.A. Baracus hates flying, so everyone who hates flying is B.A. Baracus." That's a common flaw on the LSAT, but it's not the flaw that actually happened here.
E) Just like B, this can only be the correct answer when we are given reason to believe that a source is biased. Here, the driver doesn't even mention any of his sources. Our answer is A.