I often hear him _____ ( sing ) in the next room.为什么答案上要求加ing?

I often hear him ( ) in the room I often heard him ( ) in the room I often hear him _____ ( sing ) in the next room. I often hear him _____(cough)when I pass his room. I have (hear) of him.We often hear Jay,but we didm't hear Him.A,of,from B,from,of C,abou I OFTEN HEAR HIM _ AN ENGLISH SONG ,AND YEATERDAY I HEARD HIM _ IN THE NEXT ROOM. I often hear him sing the song in the room.变为被动语态 I often hear him（）in the next room.（sing） I often hear him _____ ( sing ) in the next room.为什么答案上要求加ing? 把I often hear him play the piano all day 改为被动语态 I often hear him ( )the pop songs .A sing B sings C singing D to sing I often hear him sing the song.的被动怎么变 I often hear him sing the same song被动语态He ____ often ____ ____ sing the same song. I often hear from my pen pal .I often ____ ____ ___ ____ my pen pal .I often __ __ __ __ my penpal hear from和hear about在此题中的区别-how often do you ___ him -once a week.A hear from B hear about C come from Dask for为什么此题要选A . I often see him ___(do)some____（read）under a big tree Do not you hear of that man?___,________.I would like you to tell me about him.Do not you hear of that man?___,________.I would like you to tell me about him. I often hear him paly the piano at home.里面的那个play啊..为什么不要-s啊?!him不是第三人称单数么?!这样写什么意思啊?! I often hear the little girl ___(cry)in the morning.hear后面要不要加doing? 为什么不填crying？？