—Listen! Peter is singing in the classroom! —It be him. He has gone back to his hometown.

问题补充：

—Listen! Peter is singing in the classroom!

—It be him. He has gone back to his hometown.

A. must

B. mustn’t

C. may not

D. can’t

答案：

A. must

B. mustn’t

C. may not

(答案→)D. can’t

解析：must必须，一定；mustn’t禁止，一定不；may not不可能，表示主观的推测；can’t表示客观上的不能；句意：听，彼得正在教室里面唱歌！根据下文，他已经回他的家乡了。可知下文表示的是客观上的不可能，故选D。