“Tom graduated from college at a very young age.”“He ______ have

“Tom graduated from college at a very young age.”“He ______ have been an outstanding student.”
A、must
B、could
C、should
D、might
【正确答案】：A
【题目解析】：考察情态动词用法。Could have done本可以做某事，实际上却未做；should have done本应该做某事，实际上却为做；might have done也许做了某事；must have done一定做了某事；句意：—Tom很小的时候就大学毕业了。—啊！他一定是一个很聪明的学生。根据句意说明A正确。