----Look at the boy running on the playground. Is it David?-- It be him. I saw him go

问题补充：

----Look at the boy running on the playground. Is it David?

---- It be him. I saw him go to the teachers’ office just now.

A. mustn’t

B. can’t

C. may not

D. needn’t

答案：

A. mustn’t

(答案→)B. can’t

C. may not

D. needn’t

解析：句意：——看正在操场上跑的那个男孩，是大卫吗？——不可能是他。我刚才看见他去老师办公室了。根据句意我刚才看见他去老师办公室了，可知不可能是大卫，故选B。