题目内容
—Listen! There someone at the door.
—It must be your sister.
A. is; knocking B. is; knock
C. are; knocking D. are; knock
练习册系列答案
相关题目
题目内容
—Listen! There someone at the door.
—It must be your sister.
A. is; knocking B. is; knock
C. are; knocking D. are; knock