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。