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