The teacher told me that the students I wanted to see were seen___ football on

题目

The teacher told me that the students I wanted to see were seen___ football on
the playground just now．A playing　　　　 B to be playing　　　 C play　　　　　　D to play为什么选A

答案

see sb do sth = sb be seen to do sth (指动作已结束）
see sb doing sth = sb be seen doing sth （指动作正在进行）
根据句意：是指‘学生刚才被看见正在操场踢足球.,故正确的是A