It is hard to say what kind of person he isSometimes he is very friendly; at other times

问题补充：

It is hard to say what kind of person he is．Sometimes he is very friendly; at other times he be very cold．

A. can

B. must

C. will

D. shall

答案：

(答案→)A. can

B. must

C. will

D. shall

解析：句意：很难说他是哪种人，有时他很友好，也有时候他可能非常的冷淡。can

表示推测，意为“可能”；must表示主观看法，意为“必须、一定”； will表示意愿；shall表示征求对方意见，根据题意，故选A。