状语从句专题。
一．状语从句。
状语从句分九类：
二．状语从句详细讲解。
3.1．时间状语从句用一般现在时表示将来。连接时间状语从句的连接词有：
3.2．when，while，as均可表示“当……的时候”。
when强调“特定时间”，表示主句谓语动词的动作与从句谓语动词的动作是同时发生的，或从句的动作发生在主句的动作之前；while表示的时间是一段，而不是一点，as多用在口语中，强调“同一时间”或“一前一后”，有时还有“随着”的含义。
i'll go on with the work when／come back tomorrow．我明天回来后会继续做我的工作。
when spring came, he felt like a trip.春天来了，他想去旅游。
as spring warms the good earth，all flowers begin to bloom．(as有“随着”的含义)
3.3．till／until，表示“一直到……”主从句都用肯定式；表示“直到……才”，主句否定，从句肯定。
he worked until it was dark. 他一直工作到天黑。
he did not get up till his mother came in. 一直到母亲进来他才起床。
3.4．once“一旦”，by the time“到……时”。
once you see her, you will find what i said is true. 一旦你见到她就会发现我说的是对的。
by the time+现在时，主句用将来完成时。
by the time he arrives, we will already h**e left here. 等他到达时，我们将已离开这儿了。
by the time+一般过去时，主句用过去完成时。
by the time he arrived, we had already left here.他到达的时候我们早已离开这儿了。
3.5．as soon as，the moment表示从句动作一发生，主句动作随即发生，通常译为“一……就”。
as soon as i finish the work, i'll go to see you. 我一完成工作就会来看你。
she came to the scene the moment she heard the news.她一听到消息就来到现场。
3.6．since“自从”， before“在……前”，after“在……后”，it was not long before意为“不久”。
since引导从句用非延续性动词或“过去时间点”或“过去时间段+ago”，主句用完成时态。
since he graduated, he has worked in this city. 他毕业后一直在这个城市工作。
i h**en't seen him since last year/ three years ago. 去年以来/3年来，我没见过他。
选出最佳答案。
1) he was listening to the music, john fell asleep.
a. after b. before c. whiled. as soon as-
2) how did you try to get to school on time you missed the school bus.
a. when b. how c. why d. that
3) he was riding to school he was hit by a car this morning.
a while b. whenc. asd. so
4) lucy knew nothing about it her sister told her.
a. because b. until c. ifd. since
5) the policeman asked the child cross the street the traffic lights turned green.
a. not; when b. don't; before c. not to; until d. not to; since
6) the book was so interesting that he had read it for three hourshe realized it.
a. when b. afterc. until d. before
7) we had seen all the animals, we went home.
a. then b. after c. though d. while
8) she has made many friends she came to our school.
a. before b. after c. since d. until
9) —how long has the weather been like this?
a. until last night b. ever since last night
c. two days ago d. two days later
10) my uncle went to australia last year. we h**en't seen him
a. since almost a year b. from almost a year on
c. after almost a year d. since almost a year ago
11) he was so tired that he fell asleep he went to bed.
a. as if b. even though c. ever sinced. as soon as
12) i knew nothing about the accident my friend told me yesterday.
a. because b. since c. until d. after
13) i didn't manage to do it you had explained how.
a. until b. since c. while d. after
经典剖析】1．条件状语从句用一般现在时表示将来。引导条件状语从句的连词有：
2．表示正面的条件用if“如果”。
if you don't look after young trees, they will die very quickly.
if the museum charges for entry, a lot of people won't be able to visit it.
3．表示否定的条件用unless( =if.．．not)“除非，如果不”。
i shall not go to the cinema unless i finish my homework before eight.
说明：if…not常可以用unless替代。
if you don’t study hard, you will fail in the exam.
you will fail in the exam unless you study hard.
4．表示使某事成为现实必要的条件用on condition that“条件是”，as long as ‘‘只要”。
you may go swimming on condition that you don't swim too far away from the river bank.
as long as you don't study hard, you will fail in the exam.
5．祈使结构表条件。
前半部分的祈使结构相当于if条件句，可用动词或名词开头；后半部分的简单句常用一般将来时，有时也用一般现在时。此句型与条件状语从句形成同义结构。
give me somewhere to stand, and i will move the earth.（如果）给我一个支点，我便能掀动地球。
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