——Who is knocking at the door?——It Mr. Black because heWashington.A. cant be;has gone t

问题补充：

——Who is knocking at the door?

——It Mr. Black, because heWashington.

A. can be;has gone to

B. may be;has been to

C. must’t be;has gone to

D. may be;went

答案：

(答案→)A. can be;has gone to

B. may be;has been to

C. must’t be;has gone to

D. may be;went

解析：句意：谁在敲门？不可能是布莱克先生。因为他已经去华盛顿了。can’t be意为“不可能是”，是对事情的否定推测，has gone to sp意为“已经去了某地还没有回来”；has been to sp意为“去过某地已经回来了”；故选A。