You look very tired and you must have been preparing for the ing examination yesterday evening, you ?
A. didn’t you
B. haven’t
C. weren’t
D. hadn’t
网友回答
A. didn’t you
B. haven’t
(答案→)C. weren’t
D. hadn’t
解析：
当陈述部分带有情态动词must表示“必须”时，疑问部分用mustn’t。如：
You must work hard next term, mustn’t you?
I must answer the letter, mustn’t I?
但若表推测这层含义时，不能用must，而要根据陈述部分must之后的动词而定，如果句子中有明确的过去时间，反意疑问部分与must之后的动词有关，不可用haven’t的形式。如：
You must have made a mistake, haven’t you?
They must have seen the film last week, didn’t they?
He must be in the library, isn’t he?故本题中选C.