knock at a door和knock on a door的区别是什么
knock at a door和knock on a door的区别是什么
knock at the door 和 knock on the door有什么区别吗
there was a knock on the door.
There came a knock on the door
knock the door和knock on the door都对吧?有区别
knock at the door
they were i______ by a knock at the door
No sooner_____asleep than she heard a knock at the door
可以说there is a knock at the door吗
A knock on the door!Who --it be?
1.S_____ there was a knock on the door.
knock on与knock at的区别