—Who it be that is knocking at the door? —It be Father but I’m not sure. A. can; mustB.

问题补充：

—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

答案：

A. can; must

(答案→)B. can; may

C. must; can

D. may; must

解析：考查情态动词。Can可能；may也许。句意：——可能是谁在敲门呢？——也许是父亲，但我不确定。