She saw a lot of boys football on the playground when she walked past (经过).A. playB. to p

问题补充：

She saw a lot of boys football on the playground when she walked past (经过).

A. play

B. to play

C. played

D. playing

答案：

A. play

B. to play

C. played

(答案→)D. playing

解析：句意：当她经过的时候，看见了许多男孩子在操场上踢足球。句中有when引导的一个时间状语从句，故前面的句中用过去进行时表示看见某人正在做某事，故选D