—Must I return the book tomorrow?—No you .You can keep it for three days.A. mustn'tB. nee

问题补充：

—Must I return the book tomorrow?

—No, you .You can keep it for three days.

A. mustn

B. needn

C. can

D. may not

答案：

A. mustn

(答案→)B. needn

C. can

D. may not

解析：考察情态动词用法。A千万不能；B不必；C不可能，不能；D也许不；结合句意可知B正确。句意：—我必须明天归还这本书吗？—不，你不必；你可以再保留三天。