I think it is D.
The relative percentages of men and women who have joined the colleges is a better bet to evaluate the argument because the argument is clearly about 'The proportion of women among students' as given in the stem.
The proportion of women among students enrolled in higher education programs has increased over the past decades. This is partly shown by the fact that in 1959, only 11 percent of the women between twenty and
twenty-one were enrolled in college, while in 1981, 30 percent of the women between twenty and twenty-one were enrolled in college.
To evaluate the argument above, it would be most useful to compare 1959 and 1981 with regard to which of
the following characteristics?
(A) The percentage of women between twenty and twenty-one who were not enrolled in college
(B) The percentage of women between twenty and twenty-five who graduated from college
(C) The percentage of women who, after attending college, entered highly paid professions
(D) The percentage of men between twenty and twenty-one who were enrolled in college
(E) The percentage of men who graduated from high school
Please explain your answer choices.
Thnx & Rgds,