Mary ________ be in Paris, I saw her in town only a few minutes ago．

A.mustn't

B.shouldn't

C.can't

D.may not

答案及解析： C

解析：

“我刚才见到他在镇上，所以肯定不在巴黎，肯定推测用must，否定推测用can't do/can't have done”。