--The man in a black suit be our youth worker. I’m sure it be him. I saw him in the l

问题补充：

--The man in a black suit be our youth worker.

-- I’m sure it be him. I saw him in the laboratory building some minutes ago.

A. must; can’t

B. can; mustn’t

C. can; could

D. must; won’t

答案：

(答案→)A. must; can’t

B. can; mustn’t

C. can; could

D. must; won’t

解析：句意：那个穿黑色礼服的人一定是我们的青年工人。我确信他不是。我几分钟前在实验楼里看见他了。第一个空是一种语气比较肯定的推测，而can’t表示“不可能”，根据后面的I saw him in the laboratory building some minutes ago.可以看出，他在实验室里有可能是科技人员；故选A。