—Look at the boy running on the ground. Is it David?—It be him. I saw him go to the teach

问题补充：

—Look at the boy running on the ground. Is it David?

—It be him. I saw him go to the teacher’s office just now.

A. must

B. mustn’t

C. can’t

D. might

答案：

A. must

B. mustn’t

(答案→)C. can’t

D. might

解析：must必须，一定；mustn’t禁止；can’t不能，不可能；might可能，也许。句意：看这个在操场上跑的男孩。是戴维德吗？根据下文，我刚才看见他去老师的办公室了。可知前文表示肯定的否定语气，故选C。