英语状语从句知识点
引导条件状语从句的从属连词有if, unless (=if…not如果不……，除非), as/so long as(只要), while(=as long as只要), supposing (that)/provided /providing (that)(假如), in case(假使), on condition that(在……的条件下)等。如：
You can learn anything so long as you set your mind to learn it. 用心学本领，总能学到手。
I will go there tomorrow unless it rains.(=…if it doesn’t rain)除非下雨，否则我明天要去那儿。
He will do the work providing you pay him. 如果你能付费，他可以做这工作。
In case l forget，please remind me about it. 如果我忘了，请提醒我。
We’ll let you use the room on condition that you keep it clean and tidy. 我们可以让你使用这个房间，条件是你把它保持整洁。
注：条件状语从句和时间状语从句一样，从句的谓语动词不能用一般将来时态、过去将来时态或将来完成时，而要用相应的一般现在时、一般过去时和现在完成时态来替代。又如：
Tell me in case you get into difficulty. 遇到困难请告诉我。
Supposing he does not come, shall we go without him? 如果他不来，是不是不带他去?
但若从句谓语用了will 或 would，那 will 或 would 则是表示“愿意”的情态动词。如：
If you will go with me, I’ll wait for you. 如果你愿意等我，我们就帮你做这事儿。
谈谈状语从句的省略问题
为了简洁起见，有的状语从句(如时间状语从句、条件状语从句、方式状语从句等)有时可省略从句的主语和部分谓语(尤其是当从句主语与主句主语一致，且从句谓语包括有动词be时)：
She fell asleep while (he was) doing his homework.
他在做作业时睡着了。
While (he was) doing so, he trembled a little.
他这样做时稍稍颤抖了一下。
He opened his mouth as if (he was) to speak.
他张开口，好像要说话似的.。
Often she would weep when (she was) alone.
她一个人时，常常哭泣。
I’d like to see you whenever (it’s) convenient.
在你方便的时候我想来看看你。
If (you are) traveling north，you must change at Leeds.
如果你是向北行，你必须在里兹换车。
【注】有些由if构成的省略结构，已属固定短语，如if any, if necessary, if possible, if not, if so：
There are few, if any, mistakes in that book.
那本书就是有错误也不多。
If necessary, ring me at home.
如果必要，可以打电话到我家找我。
If possible, I wish to go there next summer.
如果可能，我希望明年夏天去。
He may be busy. If so, I’ll call later. If not, can I see him now?
他可能很忙，要是这样，我以后再来拜访。要是不忙，我现在可以见他吗?
分词作状语的主要用法
1. 表时间
Seeing the cat, the mouse ran off. 见到猫，老鼠就跑了。
The work finished, he went home. 工作做完后，他就回家了。
2. 表原因
Being very weak, she couldn't move. 她由于身体虚弱而不能行动。
His car broken down, he had to walk. 他的车坏了，所以只好走路。
3. 表条件
United, we stand; divided, we fall. 团结则存，分裂则亡。
Given more time, we could have done it better. 如果多给点时间，我们可以做得更好。
Working hard, you will succeed. 如果努力工作，你就可以成功。
Adding them all up, we can find the answer. 如果把它们加起来，我们就可以得到答案。
4. 表让步
Although living miles away, he attended the course. 虽然住在几英里以外，他仍去上课。
Defeated, he remained a popular boxer. 虽然被击败了，他仍是一个受欢迎的拳击手。
5. 表方式
He earns a living driving a truck. 他靠开卡车谋取生。
I'm returning you letter as requested. 我按要求给你退信。
6. 表伴随
He sat in the chair reading newspapers. 他坐在椅子上看报。
Don't you sit there doing nothing. 别什么也不干坐在那里。
He came in, followed by his wife. 他走了进来，后面跟着他的妻子。
7. 表结果
He fired, killing one of the passers-by. 他开枪了，打死了一个过路人。
He died, leaving his wife with five children. 他死了，留下他妻子和五个儿子。
It rained and rained, vehicles bogged and bridges washed out. 雨不停地下，车辆陷入泥沼，桥梁被水冲去。
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