【题目】—It’s already 11 o’clock , and he ______ have been here half an hour ago.
—Maybe he got caught in the rain.
A. must B. ought to
C. may D. can
在线课程【答案】B
【解析】
考查情态动词。句意：已经11点了，他半小时前就该到了。A. must have done必定做了…（表示对过去的推测）；B. ought to have done 本应该做的；C. may have done可能已经做过某事；D. can have done本来可以做的（但没有做），根据题意，故选B。