Since 1986 enrollments of African Americans, American Indians, and Hispanic
Americans in full-time engineering programs in the United States has steadily increased,
while the number of other students who enter the field has fallen.(A) has steadily increased, while the number of other students who enter the field has
fallen
(B) has steadily increased, while other students entering the field have declined in
number.
(C) increased steadily, while there was a decline in the number of other students
entering the field
(D) have steadily increased, while the number of other students entering the field has
fallen
(E) have steadily increased, while that of other students who enter the field fell

OA is D
[spoiler]Is the subject of the sentence not enrollments? I felt the answer was B, what's wrong with my thinking?[/spoiler]