（一）时间状语从句
(1) 时态上遵循“主将从现(主句是将来时，从句是现在时)”的原则，即“一般将来时+一般现在时”“过去将来时+一般过去时”。
(2) when经典句式“过去进行时+when+一般过去式”，while经典句式“一般过去式/过去进行时+while+过去进行时”。
(3) as“一边……一边”。
例如：John sings as he walks home.
(4)before，after。
例如：— Jenny, will you leave for the USA now?
— No. It will be two weeks before I leave here.
(5) since经典句式“现在完成时+since+一般过去式”。
例如：We have been friends since we met in Beijing.
(6) until/ till，not… until。
例如：I won’t believe it until I see it with my own eyes.
[玫瑰]until/till引导的时间状语从句状语从句有哪几种，如果主句谓语动词是延续性动词，主句是肯定句或否定句都可以；但是果主句的谓语动词是非延续性动词状语从句有哪几种，则主句只能是否定句。
例如：I didn’t go to bed until I finished my homework.
(7)as soon as“一…就…”。
例如：I will call you as soon as I get the tickets to the movie.
（二）地点状语从句
连接词有where、wherever等。
例如：Put your coat where you can easily find it.
You can sit wherever you like.
（三）原因状语从句
连接词有because，as ，since（既然）等。
例如：Because the book was expensive, I didn’t buy it.
=The book was expensive, so I didn’t buy it.
（ because和so不能同在一个句子里。）
As I don’t know the way, I had to ask the policeman.
Since you are free,why not go shopping with me?
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