That problem aside, it's a tricky question because there are two different voices --- Moviemania, and the critic of Moviemania. Here's the argument

(1) Background facts: "In January of last year the Moviemania chain of movie theaters started preparing its popcorn in canola oil, instead of the less healthful coconut oil that it had been using until then. Now Moviemania is planning to switch back." (Everyone agrees about these.)

(2) MOVIEMANIA: [We are switching back to canola oil because] the change has hurt popcorn sales.

(3) Critic: That claim (#2) is false, however, since according to Moviemania’s own sales figures, Moviemania sold 5 percent more popcorn last year than in the previous year.

Then the question says, "Which of the following, if true, most strongly supports the argument (#3) against Moviemania’s claim (#2)?

So, we want something that will weaken Moviemania's argument, and strengthen the argument of the critic.

(A) Total sales of all refreshments at Moviemania’s movie theaters increased by less than 5 percent last year.
If the other refreshments increased by less than 5%, but popcorn increase 5%, then popcorn outperformed the other refreshments. This means, popcorn sales were not hurt, relative to other refreshments. This weakens Moviemania's position, and strengthens' the critic, so this is the correct answer.

(B) is irrelevant

(C) & (D) & (E) all strengthen Moviemania's position, in one way or another, so these do the opposite of what the question asks.