(·江西)It be the postman at the door.It's only six o'clock.A. mustn'tB. can'tC. won'tD.

问题补充：

(·江西)It be the postman at the door.Its only six oclock.

A. mustn

B. can

C. won

D. needn

答案：

A. mustn

(答案→)B. can

C. won

D. needn

解析：根据Its only six oclock推知，那不可能是邮递员，否定形式推测要用can 或couldn 。因为must表推测时，只能用于肯定句。