someone____at the door while Tom was having his supper.A.was knocking B.has knocked C.is knocking D.knocked 我选的A,但老师说是错的.是否选D?若是when结果是否不同?

分类: 作业答案 • 2022-01-02 12:35:31

问题描述：

someone____at the door while Tom was having his supper.
A.was knocking B.has knocked C.is knocking D.knocked 我选的A,但老师说是错的.是否选D?若是when结果是否不同?

答

的确选D
while后面才接ing形式,而这里因为是过去发生的所以用过去时