Explanation

Reading the question: when we read this question, it may be difficult to avoid reading the answer choices, the questions, without having made a prediction first. But this impulse can be counterproductive, because the less helpful the answer choices are, the more you'll need an exact filter, such as a prediction, to evaluate them.

Creating a filter: the stem says, What's the most serious weakness in the explanation described above? We try to get more specific about what exactly the explanation is. It's the view of the individuals with blindsight. There are two things stated: they are not surprised, and they attribute their unusual abilities to coincidence. We're not sure whether both parts are the explanation or just the coincidence part. It must be the coincidence part: that's an opinion, whereas the lack of surprise is more a feeling. So, the right answer will undermine the idea that this is really happening by coincidence. That's our filter, the critical detail.

Applying the filter: Which answer choices undermine coincidence? Choice (A) does; it attacks the coincidence theory. (B) and (C) focus on the attitudes of the people with blindsight, not the coincidence explanation, so we will knock them out. (D) is trying to redefine what coincidence is, and it appears to take as granted that the individuals are not functionally totally blind, but they believe that they are. So (D) is out. Choice (E) does not attack the coincidence explanation. Coincidental events do happen repeatedly; some repetition, in and of itself, is not odd. It's rather that these coincidences happen so much more often than with people who are originally blind. That rules out (E) and leads us straight back to (A), which must be the correct answer. The correct answer is (A).