--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
网友回答
(答案→)A. must; can’t
B. can; mustn’t
C. can; could
D. must; won’t
解析：句意：那个穿黑色西装的人肯定是我们的青少年辅导员。我确定不可能是他，我几分钟前看到他在实验楼里。must肯定; can’t不可能，故选A