I often see Tom on the playground. When I passed the playground yesterday I saw him . A.

问题补充：

I often see Tom on the playground. When I passed the playground yesterday, I saw him .

A. play; playing B. to play; play C. playing; to play C. playing; play

答案：

解析：看某人做某事表示状态或情况用see sb do sth，我经常看到汤姆在操场上玩，指的是一件事，而不是动作，故第一个空用play，后句当我经过操场的时候，看到他在玩应该正在玩，故用see sb doing sth，故选A.