Question

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

1. A.
   mustn't
2. B.
   shouldn't
3. C.
   can't
4. D.
   may not

Answer 1

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”。