knock的介词和副词短语有哪些
1、knock at 该短语表示“敲(门、窗等)”。有时,knock也会用作名词,表示“敲击”,后面也是紧跟介词at。如: He wondered whether it would be proper to knock at her door. (他不知道敲她的门是否恰当。) I was preparing for bed when I heard a knock at the door. (我正准备睡觉时听到有人敲门。) 2、knock...off 该短语表示“把...撞倒”...