Suddenly there was another knock at the door.
突然，又有人敲門。
Just as breakfast was completed there was a knock at the door.
早飯剛吃完，有人敲門。
Just when she was going to bed, there was a knock at the door.
正當她要上床睡覺時，有人敲門。
Ring the doorbell or knock at the door before you enter the room.
在你進入房間之前，按一下門鈴或敲門。