2012大学英语四级语法：时间状语从句

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时间状语从句 　　时间状语从句主要由以下连词引导：when, whenever, as, while, since, until, till, before, after, as soon as, once, hardly (scarcely) … when, no sooner … than。
　　I will discuss the matter with you when we meet tomorrow.
　　He didn’t go to sleep until he finished doing his homework.中华考试网(www．Examw。com)
- u/ ^+ ^3 \0 z  i2 y" [' {( g　　You have changed a lot since we met last time.
0 p; q; [/ _1 W$ O　　时间状语从句还可由某些可充当连词的名词(the moment, the instant, every time,等)和副词(instantly, directly等)引导：
　　I will tell you the news the instant I know.
9 b# J5 e7 }' k  P# q　　Directly the teacher came in everyone was quiet.
　　Note:
　　① before除了可表示 “在…之前”外，还可用来强调主句所表达的时间、距离很长或花费的力量相比较大，可译为“…才”。(“not … before” 可用来强调主句所表达的时间、距离很短或花费的力量相比较小，可译为“…就”)。
　　It was a long time before I got to sleep again.
　　They had not been married a month before they quarreled.wｗw.ExamＷ.CoM
/ [& N$ N3 Q- V. Y/ A& C　　② 如果位于when引导的分句之前的主句使用过去进行时、过去完成时或“was/were about to, was/were on the point of”等结构时，when表示突然发生某事，可译为“正在…突然”或“刚…就”等。这时，不能够用as或while来代替when。
　　I was walking on the street when I ran into my old friend John.
　　She had just fallen asleep when the telephone rang.
# T3 a! J2 Y# [7 ]3 x6 J　　We were about to leave when it began to rain.