She saw some boys ____ soccer on the playground when she was on the way to the classroom

题目

She saw some boys ____ soccer on the playground when she was on the way to the classroom
A.played B.to play C.playing
横线上该填什么,为什么呢
还有There are many children playing.
为什么playing前没有加be动词,说出道理,出现这种情况的句子该怎么用,那种句子才用到这种情况
真心求知,
可是saw是see的过式呀

答案

C,考察了一个短语的用法：see sb doing sth指看到某人正在做某事
see还有一个用法：see sb do sth,指看到某人做某事的全过程
There be +sb doing sth,这是一个固定用法,意为：那儿有某人正在做某事