When I got there I saw some boys on the playground.A. playingB. playedC. to playD. was w

问题补充：

When I got there ,I saw some boys on the playground.

A. playing

B. played

C. to play

D. was waiting

答案：

(答案→)A. playing

B. played

C. to play

D. was waiting

解析：此题重点考察固定结构see sb doing sth 看到某人正在做某事