I heard him (knock, knocking) three times 选哪个,为

I heard him knock three times.我听见他敲了三次,这个knock为什么不用过去式? I heard someone _____(knock /knocking) at the door just now i was watching tv when i heard the door(knocking) I called him three times last night,but it was s_____ that h I cried three times today I heard him singing when I pass his room.改被动（主语为he） I exercise three ( times) a day. he has three times ____than i have 将Eng文翻下.One day about a week ago,I heard someone knocking at I heard someone ____(knocking/knocked)at the door just now. 将Eng文翻下啦谢谢One day about a week ago,I heard someone knocking （watch) a TV play ,I heard someone knocking at the window.句首