问题补充:
There is no light in the room. They must have gone to the lecture.?
A. didn’t they
B. haven’t they
C. don’t they
D. mustn’t they
答案:
A. didn’t they
(答案→)B. haven’t they
C. don’t they
D. mustn’t they
解析: 本题是一个反义疑问句,前句是肯定的句子,后句应该用否定的结构+人称,前句的助动词是have,故用其否定形式haven’t,故本题选B。