When did you first visit China?I think it _____in 1996,when my parents were teaching in YunnanUniversity.A.must be B.should have been C.may be D.must have been其余选项为什么不对,尤其是A?

问题描述:

When did you first visit China?I think it _____in 1996,when my parents were teaching in Yunnan
University.
A.must be B.should have been C.may be D.must have been
其余选项为什么不对,尤其是A?

d应该是正确的

一定是在1996年
对过去发生的事的肯定猜测,所以must后要用完成式(表示过去的事)。
A选项,must be是说现在的事

表示对过去的推测,用情态动词+ have done的形式.所以排除A,C.而B表示的意思是本该做某事而没做,不符合题意,所以选择D.