2012年12月大学英语四级语法：比较状语从句

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2012年12月大学英语四级语法：比较状语从句
比较状语从句：
* c; P# X# N0 H# O6 X　　than, as…as…，not so as…，（not) the same as, the+比较级；
　　eg：Light travels fast than sound.
　　the+比较级：
% u1 `. S1 T9 S" u1 n) S2 n　　eg：The sooner，the better.
7 n( l6 p% c% z+ X  `* M) _  p* ]　　eg：Girls are thus seen as less valuable than boys and art kept at home to do housework while their brothers are sent to school - the prophecy（预言) becomes self- fulfilling, trapping women in a vicious circle (恶性循环) of neglect.
　　（1）当……的时候：while, when, as ；
$ Y8 O/ `, Z7 z; k; ?8 Y　　when：强调一件事情正在发生的时候，另外一件事情突然发生；
; G) P, v0 W, ]8 o8 g; {　　eg：When I was watching TV, my mother came back.
; z; p0 |( H2 k/ p8 a' D　　while：强调两个动作同时进行，一边……一边……；
3 C4 U$ ~) _! ]5 U( S/ S5 w9 y! F　　eg：My father is cooking while my mother is reading newspaper. 中华考试网
5 [% B) z2 V' k: e: M　　as："随时间推移"
　　eg：As time went by, the days became longer and longer.
　　（2）一……就……：as soon as ,主将从现；用directly，immediately, instantly连接两个句子；一些名词如the minute，the moment, the instant也可表示；no sooner… than, hardly… when后面的句子需要倒装；
/ y9 H0 y& V* r3 m8 {5 H　　eg：I will write to you the moment/minute I arrived in Paris.
3 o0 [+ w5 D6 [( d: I3 H　　（3）特殊单词：by the time that, every/each time（使用时后面不要再加when）
　　（4）till＆until：
　　① 肯定形式表示的意思是"做某事直至某时"，动词必须是延续性的；
* Y  F4 Y1 v; k/ I　　否定形式表达的意思是"直至某时才做某事"，一般用until，动词为延续性或非延续性都可以；
　　eg: I slept until midnight.
　　Wait till I call you.
　　She didn’t arrive until 6 o’clock.
　　② Until可用于句首，而till通常不用于句首，通常用于句中；
: q1 N, N5 L: n; a+ V9 o2 E　　eg: Until you told me, I had heard nothing of what happened.
　　eg：As you sleep you pass through a sequence of sleep states—light sleep, deep sleep and REM (rapid eye movement) sleep—that repeats approximately every 90 minutes.