I did not hear the phone,I___asleep.A.must be B.must have been C.should be D.should have been

问题描述:

I did not hear the phone,I___asleep.A.must be B.must have been C.should be D.should have been

选B
must have been 是对过去的猜测,我没听见电话响,我一定是睡着了.那A不行吗?A表示对现在的推测,而前一句用的是过去式。