Premise: undergraduate students who had received at least a B+ were qualify for honor class.
Premise: A reduction in undergraduate enrollment
Conclusion: the percentage of failing grades in the honors class would reduce.
Assumption: Before a reduction in enrollment, the number of undergraduates failing grades (scored lower than B+) accounted for the large percentage of all applicant.
(A)
Graduate students all scored at least B+ in composition
Wrong. we're talking about undergraduates, not graduates.
(B)The honors creative writing course is experiencing overcrowding due to increases in
graduate enrollment.
Wrong. we're talking about undergraduates, not graduates.
(C)Many undergraduates would work harder to score B+ in composition rather than be excluded from honors creative writing
Wrong. Shell game. key word is "excluded from honors" ==> it means those undergraduates were already in honors class. They just work hard to avoid excluding from honors class.
(D)The
number of failing grades in honors creative writing has decreased in recent years.
Wrong. Out of scope.
(E)Undergraduates who scored lower than B+ in composition are responsible for a disproportionate percentage of failing grades in honors creative writing.
Correct. This is exactly the assumption above. Before a reduction in enrollment, the number of undergraduates failing grades (scored lower than B+) accounted for the large percentage of all applicant. After the reduction, the number of undergraduates failing grades applies for honors class reduces ==> the percentage of failing grades would reduce.
Hope it helps.