This morning when I walked by the park I saw many children there.A. playedB. playingC. p

问题补充：

This morning when I walked by the park, I saw many children there.

A. played

B. playing

C. play

D. to play

答案：

A. played

(答案→)B. playing

C. play

D. to play

解析：句子中“saw”为感官动词，句型为“see sb. do/doing sth.”,当我路过公园时，看见孩子们正做某事，故选B。