—Who it be that is knocking at the door?
—It be Father, but I’m not sure.
A. can; must
B. can; may
C. must; can
D. may; must
网友回答
A. can; must
(答案→)B. can; may
C. must; can
D. may; must
解析：考查情态动词。第一句话：可能是谁在敲门？是一个强调句型的特殊疑问句。It can be …..that….。第二空是情态动词表示推测，后半句有but I’m not sure，说明不确定，应该用may.所以选择B。