单选题 ______ in universities around the nation has more than tripled compared to this time last year.
A. Enroll B. Enrolls
C. Enrolling D. Enrolhnent

【正确答案】 D
【答案解析】[解析] 全国大学的入学人数已经是去年同期的三倍多了。本题要求选择enroll的适当词形。故选D。