—Will you stay for some more days? —Sorry I. My mother called to ask me to go back at onc

问题补充：

—Will you stay for some more days?

—Sorry, I. My mother called to ask me to go back at once.

A. mustn’t

B. may not

C. can’t

D. wouldn’t

答案：

A. mustn’t

B. may not

(答案→)C. can’t

D. wouldn’t

解析：情态动词表推测。句意：－你再呆几天好吗？－对不起，我不能，我的母亲打电话让我马上回去。Mustn’t禁止；may not可能不；wouldn’t不愿做……，将要不……。故选C。