I saw them basketball at this time yesterday.A. playB. playedC. to playD. playing

问题补充：

I saw them basketball at this time yesterday.

A. play

B. played

C. to play

D. playing

答案：

A. play

B. played

C. to play

(答案→)D. playing

解析：考查感官动词。感官动词后跟do或doing，跟do表示看到的全过程或经常性、习惯性的动作；跟doing则表示看到一瞬间的动作。因为“昨天这个时候”是过去的点时间，点时间正在发生的动作用doing.