. - The speaker is a tall man with glasses. - Then it be Mr. Smith who is short and thin.

问题补充：

. - The speaker is a tall man with glasses.

- Then it be Mr. Smith, who is short and thin.

A. wouldn

B. won

C. mustn

D. can

答案：

A. wouldn

B. won

C. mustn

(答案→)D. can

解析：句意：上文，这个说话的人是一个戴着眼镜的高个子男子。下文，那不可能是史密斯先生，史密斯先生又矮又瘦。表示推测，用can ，选D。