He got a nasty knock on the head.

　　他頭部遭到重重一擊。

　　There was a sharp knock on the door.

　　敲門聲大作。

　　No sooner had I sat down than there was a loud knock on the door.

　　我剛坐下就有人大聲敲門。

　　He went up the garden path to knock on the door.

　　他穿過花園小徑去敲門。

　　If you haven't made an appointment, take pot luck and knock on the door

　　如果你沒有預約，就敲門試試運氣吧。