第1个回答 2009-03-22
Please knock before you enter
第2个回答 2009-03-22
Please knock before you come in the room/house
看你说的是房间还是房子
第3个回答 2009-03-22
ls的都有问题嘛~~
应该是Please knock at the door before you enter the room
第4个回答 2009-03-22
Please knock at the door before you are in.