i often hear her （）after class.答案是sing,我认为应该填to sing啊,应为hear

i often hear her （）after class.答案是sing,我认为应该填to sing啊,应为hear I often hear her sing this song I often hear birds ( )in the morning?是填to sing 还是填singi I often hear John (sing/singing/to sing)in his room.为什么这里要填s 一堆英语问题（一）1I often hear him ________ in the room 是填sing还是sing I‘ve often heard her sing this song.与I often hear her sing t I often hear her sing the song.(改为被动语态) i often hear her sing a song变被动句 I often hear the lonely girl sing in her room I often hear her sing.变成被动语态 she ( ) often ( )【hear】to sing in her room I often hear her _(sing) in the morning ,填什么?为什么