Question

【题目】—It's already twelve o'clock, and he ____________ have been here half an hour ago.
—Maybe his flight was behind time.
A.must
B.ought to
C.may
D.can

Answer 1

【答案】B
【解析】句意：——现在已经12点了。他半个小时之前就应该到这儿了。——也许他的飞机晚点了。根据对话内容，尤其是＂Maybe his flight was behind time.＂可知，用ought to/should have done sth结构表示＂过去本应该做某事而实际上没有做＂。故选B。