21.He was ___ by the sound of the back door opening in the d

21.He was ___ by the sound of the back door opening in the d Keys ( ) opening the lock in the door. go in for politics;He went in by the back door I tried opening the back door,but it was locked,too.其中lock为什 the key is used by people for opening the door 】 The key ____ for opening the door of the room. ___ he was out of the room,he turned back and knocked at the He slept with the door ___ yesterday.A open B.opening C.open ＿ the sound of the knocking on the door,he rose and went to Tony,___ the door,please.A.open B.opens C.opening D.to open he stood at back of the door.哪里错了, Lily is opening the door.(对opening the door提问)