We saw her play the piano at the party.这句话里play为什么用原形呢?

We saw her play the piano at the party.这句话里play为什么用原形呢? I saw Li Yundi play the piano last concert.为什么这里用原形play she can play the piano her siser can play the piano,too 用(bo We saw Sally play the piano in the music club.请把这句子改成被动语态. 初中英语see用法如题He saw her （playing/play） the piano when he passe We play happily at the party的同义句 play the piano or play piano? play piano or play the piano? I saw him ____(play)the piano this time yesterday. I saw him_____(play) the piano slmost every day. he play the piano every day这句话对吗 We often plays in the playgound为什么play后面加s,不是应该用原形吗?