Critical Reasoning

If participation in the honors creative writing class were limited to graduate students and those undergraduates who had received at least a B+ in composition, most of the undergraduate students would be forced to take the regular creative writing class. Such a reduction in undergraduate enrollment would reduce the percentage of failing grades in the honors class.
Which of the following, if true, would most strengthen the conclusion drawn in Sentence 2 above?

(a)Graduate students have all scored at least B+ in composition.
(b)The honors creative writing course is experiencing overcrowding due to increases in graduate enrollment.
(c)Many undergraduates would work harder to score B+ in composition rather than he excluded from honors creative writing. (d)The number of failing grades in honors creative writing has decreased in recent years.
(e)Undergraduates who scored lower than B+ in composition are responsible for a disproportionate percentage of failing grades in honors creative writing.

This is a question from kaplan premier.

The OA is E but please carefully have a look at A.

The correct choice is no doubt a strengthener but the other choice which i mention, would it not count as a
Defender in the Supporter-Defender assumption model, if this were a assumption question.

I ask this question as there is a very thin line between an assumption and a strengthen question.