Please knock at the door ________ you come into the room Wap版

试题详情及答案解析

Please knock at the door ________ you come into the room.

A．before

B．after

C．until

D．while

答案：A

试题分析：句意:在你进入房间之前请先敲门。before 在……之前；after 在……之后；until 直到……时候；while 当……时候。根据句意可知，进入房间之前敲门，故选A。
考点：考查连词。