题干
.
—Who______ it be that is knocking at the door?
—It ______ be Father, but I’m not sure.
—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; ca
D：may; must
答案(点此获取答案解析）
B
