—Look! The man at the gate ______ be our headmaster. He is always standing there every morning.—No, it ______be him. He is holding a meeting in the office now.

题型：单选题题类：常考题难易度：普通

—Look! The man at the gate ______ be our headmaster. He is always standing there every morning.
—No, it ______be him. He is holding a meeting in the office now.

A、must, can't B、must, mustn't C、can't, can't D、can't, mustn't