A researcher studying lawyers found that, on average,

This question doesn't make a lot of sense. First, there's an incomplete comparison in the question: "students who take philosophy classes are more likely to become lawyers." More likely than what? That sentence could mean two different things: "students who take philosophy classes are more likely to become lawyers than are students who don't take philosophy", or "students who take philosophy classes are more likely to become lawyers than they are to become something else". If this were a Sentence Correction question, we'd need to fix that sentence.

So it isn't even clear what conclusion we're trying to weaken. Second, the question is clearly designed to test reversal of causality - the researcher concludes that philosophy courses lead people to want to become lawyers, but it's just as possible that wanting to become a lawyer leads people to take philosophy courses - but the setup is flawed. The question is based on measuring a probability: the probability that someone in a philosophy class will become a lawyer. One completely natural way to assess that probability is to consider the percentage of philosophy students who go on to become lawyers. If you look at that percentage, then it makes no difference *why* the students took philosophy. If philosophy courses are very popular among people who want to become lawyers, then naturally one would expect, choosing a random philosophy student, that it is likely he or she will become a lawyer. It's only if you measure that probability in an unnatural way that the argument suffers from a reversal of causality error. That is, it's only if the conclusion is that "if someone randomly enrolls in a philosophy course, he or she will become more likely to then pursue a legal career than if he or she did not enroll in the philosophy course" that you have the reversal of causality error that this question is getting at.

It's not a good question. Where is it from?