Question

The children ________ on the playing ground when I left school.

A. played
B. are playing
C. was playing
D. were playing

Answer 1

答案D
精析：此句是个复合句。以when引导的时间状语从句，从句动作发生在过去，而主语的动作发生在从句动作的当时，因此主句的谓语动词用过去进行时，其结构是“was/were+动词的现在分词”。此句中的主语children是复数，因此选择were playing。