— It be Jack who is in the office.
— No, it be him. I saw him off at the airport half an hour ago.
A. can’t ; can’t
B. must; can’t
C. must; mustn’t
D. may; mustn’t
网友回答
A. can’t ; can’t
(答案→)B. must; can’t
C. must; mustn’t
D. may; mustn’t
解析：must表推测只用于肯定句；在否定句和疑问句中用can。