In a Strengthen question, we need to find an answer choice that when combined with the reasoning in provided in the stimulus, will support the conclusion.
This stimulus concludes that it is not due to the negative reviews that the film had a small audience, it is rather due to other competing films being played at the same time as the opening of this film.
We need to find an answer choice that will bolster the idea that it is due to the other films, and not the negative reviews, that caused the small audience for the movie under question.
Answer choice B does exactly this by stating that people typically watch a maximum of one movie per weekend. If this is the case, then having already gone to see the competing movies, many moviegoers would not then see the film director's movie that weekend. It is no longer the fault of the negative reviews.
I hope this helps, please let me know if you have any further questions.