Someone is knocking at the door. It () my

问题单项选择题

Someone is knocking at the door. It () my mother. It's time for her to be back.

A．can he

B．may not he

C．must be

D．mustn't be

答案

参考答案：C

解析：

情态动词中的must，can，could，may都表推测。其中must的可能性最大，can次之，may最小。由该句话的语境可以推断出，一定是我妈妈回来了。故选C。