Question

（2007天津宝坻一模模拟）I didn't hear the bell ring; I ________ asleep.

1. A.
   must be
2. B.
   must have been
3. C.
   should be
4. D.
   should have been

Answer 1

B
句意：我那时没有听到铃响，一定是睡着了。根据前面didn't hear...的提示，可知本题是对过去状态的推测，故排除A、C两项；表肯定推测B符合题意，而D表示本应该做而实际没有做的概念。