The stimulus says, "Audiences will therefore judge the performances of Method actors to be more realistic than the performances of traditional actors."
D says that traditional actors do not aim to produce performances that are realistic representations... that's not true at all. They could still aim to do so, it's just that Method actors do a more realistic job.
Try the assumption negation technique for B... if the behavior that results when a Method actor feels a certain emotion DOES NOT conform to the behavior that is generally associated, then according to the criteria necessary to judge something realistic stated in the first sentence, then the audience won't associate with the emotional states, thus making it not realistic, thus destroying the whole argument.
I hope that explains it well.