someone is knocking at the door
有人敲门了。
Someone’s at the door.
有人敲门吗？
Is someone knocking at the door?
没有，有人敲门，但走错了
No, someone knocked on the door, but they had the wrong place.
— 镜子 (1975)
有人敲门
Someone is knocking at the door.
— 虎口脱险 (1966)