Explanation

Reading the question: this prompt, much like Topeka Flights, exhibits some of the features of an argument but is more like an "explain" question. If you are studying with GMAT books and materials from other sources, be aware that most of them overemphasize the importance of arguments in Critical Reasoning. Arguments are certainly essential to Critical Reasoning, but actual questions often focus on other aspects of reasoning.

Note: we can take the opportunity to highlight the fact that, if you are stumped by a prompt or can't create a filter, you can try going straight to the negation test. We need to understand the essence of the prompt--sales are down, reviews are negative, and there are complaints from people who have read the review--but from there we can move straight to the answer choices.

Logical proof: we're asked for an answer that strengthens, so the correct answer, when negated, will weaken or destroy the argument. Choice (A): if other companies did not report similar reductions in sales, it wouldn't strongly weaken the argument; there are still a variety of possible problems at this company. So choice (A) is not highly material to the situation. Choice (B): if the complainers did not remain regular buys of the cars, then they probably dropped the product. That would weaken the claim, because in that case the review did ultimately cause the drop-off in sales. So choice (B) is probably our answer. Choice (C), when negated, doesn't lead to anything sensible. Choice (D): suppose this was the first time this company had been in a situation like this. That wouldn't help us determine either way whether the company's claim is accurate. Choice (E), if negated, would indicate that car buys do not rely on reviews. That statement strongly strengthens the carmaker's argument, so Choice (E), when not negated, strongly weakens the argument--and we want a strengthener. So choice (E) is exactly wrong. Only one answer choice passed the negation test. The correct answer is (B).