—Look! The man at the gatebe our headmaster. He stands there every morning.—No it be him.

问题补充：

—Look! The man at the gatebe our headmaster. He stands there every morning.

—No, it be him. He is holding a meeting in the office now.

A. must； can’t

B. must; can

C. can’t; mustn’t

D. can’ t; must

答案：

(答案→)A. must； can’t

B. must; can

C. can’t; mustn’t

D. can’ t; must

解析：考查情态动词表推测的用法。must表推测用于肯定句中,can表推测用于疑问或否定句中。根据题意应选A。