---There is somebody knocking at the door. Who it be?
---I’m not sure. It be a postman.
A. may; must
B. will; can
C. can; may
D. may; will
网友回答
A. may; must
B. will; can
(答案→)C. can; may
D. may; will
解析：may可以，可能；must必须，一定；will将要；can能，可能。句意：有人在敲门。可能是谁？——我不确定。可能是邮递员。结合语境可知选C。