英语动词不定式和状语从句用法

英语动词不定式和状语从句用法
英语动词不定式中什么时候做状语,表语,主语,宾语的补足语,定语?从句中while,when,as ,until等等（还有的忘记了）的用法?如何判断?

不定式是历次大学英语四级考试必考的内容.不定式在句子中可做主语、宾语、表语、定语、状语和宾语补语.
1）不定式做主语一般表示具体的某次动作.
【例如】
to complete the 30 storied building in one year was quite a difficult task.
to do that implies taking responsibility.
当主语较长,谓语较短时,常用it做形式主语,而将不定式放到谓语的后面.
【例如】
it is important for modern young people to master at least two foreign languages.
it做形式主语,不定式放在谓语动词之后常用于下列结构中：
a） it is＋形容词（easy, important, difficult, foolish, inconvenient, unnecessary, right, wrong...）＋（ for/of sb.）＋不定式
【例如】
it is essential to reserve a table in advance of christmas eve.
it is hard to put my hopessintoswords.
it is not easy to catch fish with your hands only.
it is important for us young people to learn english and master it.
b） it is＋名词（a pleasure, a pity, a pleasant thing, one’s duty, an honor, a shame, a crime, no easy job...）＋不定式
it is a sheer waste of time to read that kind of trash.
it is a pity to have to go without her.
it is a glorious death to die for the people.
c） it takes （sb.） some time （hours, months, days, a lot of time, patience...）＋不定式
it takes me three hours to learn english each day.
it took them half the night to get home in the snow.
2）不定式作表语不定式作表语常表示将来的动作,主语常常是表示意向、打算、计划的词,如wish, idea, task, purpose, duty, job等.
【例如】
the most important thing for one’s health is to have plenty of exercise.
my chief purpose has been to point out the difficulties of the matter.
the purpose of the organization is to greet all new comers to the city and to provide them with any necessary information.
what i wanted was to get the work done as quickly as possible.
3）不定式作宾语不定式常在下列动词后面作宾语：
　
afford, agree, apply, arrange, ask, attempt, beg, begin, care, choose, claim, consent, demand, decide, desire, determine, expect, fail, hope, hesitate, hate, intend, learn, like, manage, mean, neglect, offer, plan, prepare pretend, promise, refuse, resolve, seek, tend, threaten, want等.
【例如】
i like to go out for walks in the warm sunshine in spring.
my mother hates to move from place to place, for she feels tired.i decide to work hard and get doctor’s degree.
the room is designed to be my study, but now it has to be used as a bedroom for the children.
she failed to finish the assignment in time, and she was worried about it.
there is a man at the reception desk who seems very angry and i think he means（ ）trouble. （cet-4 1997, 1）
a） making
b） to make
c） to have made
d）shavingsmade
mean后面一般加不定式,所以a和d可以排除.根据句意,他看起来非常生气,他想找麻烦,不定式的动作还没有实施,应用一般式,因此答案为b.不定式作宾语还常用在下面结构中；主语＋动词＋it＋形容词＋不定式.
【例如】
we found it impossible to get everything ready in time. i think it important to learn english well in college. 使用这种句型的常见动词有：believe, consider, declare, feel, find, guess, imagine, prove, realize, suppose, think,等.
4）“whword＋不定式”结构不定式前加一个疑问代词（what, which, who, whom, whose）或疑问副词（where, when, how, why）,以及连词whether构成特殊的不定式短语,其作用相当于一个从句,这样的不定式短语常在某些动词后面作宾语.
常见的可以接这种不定式短语的动词有：
know, see, decide, tell, ask, consider, discover, explain, findout, forget, guess, hear, imagine, inquire, learn, observe, perceive, remember, think, understand, wonder等.
【例如】
i couldn’t decide which book to choose. i can tell youswheresto get this book.they found it hard to decide whether to go swimming next sunday or to visit aunt sally in new year. “whword+不定式”结构除了作宾语外,还可以在句中作主语或者表语. 状语从句：
用一个句子（从句）来作另一个句子（主句）的状语,用作状语的句子就叫作状语从句.作什么样的状语就叫什么类型的状语从句.例如：条件状语从句就是用一个句子来作条件状语.
状语从句的分类：
（1）时间状语从句
凡是从句都必须有引导词,引导时间状语从句的词有when,before,after,until,as soon as,while 等.
（2）条件状语从句
主要看一下由if引导的条件状语从句.if 意为“如果”,引导条件状语从句时,表示假如有从句的动作发生就（不）会有主句的动作发生.例如：
If it doesn't rain tomorrow,we will go there by bike.如果明天不下雨,我们就骑自行车去那里.
If I get there early,I can see the doctor quickly.如果我早早地到那里,我就可以快点看病.
3）地点状语从句用法要点
常用where（哪里）和wherever（无论哪里）eg.
Where there is a will,there is a way. 有志者,事竟成.
We will go wherever the motherland need us most. 我们要到祖国最需要的地方去.
（4）原因状语从句用法要点
常用的引导连词有because,as和since,三者的区别是：在回答问题的时候,使用because；对于显而易见的原因,常用as或since；as和since的从句常放在主句之前,而because的从句常放在主句之后.eg.
Why did you go? I went because Tom told me to go. 你为何去?那是因为汤姆叫我去.
He was angry not because we were late but because we made a noise.
他很生气不是因为我们来迟了,而是因为我们弄出了声音.
As it was raining hard,we had to be indoors. 由于雨太大,我们只好呆在家里.
Since you feel ill,you'd better not go to work. 既然你感觉不舒服,你最好不要去上班了.
（5）目的状语从句用法要点
常用的引导连词有so that,that和in order that译为：以便,为了,目的是.eg.
Please speak more slowly so that we can make full notes. 请讲慢一点,以便我们能作详细笔记.
I shall write down your address that I may not forget. 我要把你的地址记下来,以免忘记.
I sent the letter by air mail in order that it might reach him in time. 这封信我以航空信发出,以便他能及时收到.
注：目的状语从句可以用动词不定式来替换做目的状语.eg.
We work harder than usual finish it in a week. 我们比平常加倍努力工作以在一周内完成工作.
三、主句与从句时态一致的问题.
在时间状语从句和条件状语从句中,主句和从句之间的时态一致问题一般分下列两种情况：
1. 若主句是祈使句,或主句中有情态动词,或主句中谓语动词是一般将来时,那么从句用一般现在时表示一般将来时.例如：
Be careful when you cross the road. 过马路时要小心.
Put up your hand if you have any questions to ask. 如果你们有问题要问的话,请举手.
The traffic must stop when the lights are red. 红灯亮时,车辆必须停下.
2. 若主从句谓语动词都是陈述过去,那么主从句都可以用一般过去时.例如：
She could sing when she was four years old. 她四岁的时候就会唱歌.
宾语从句：
宾语从句是用来充当宾语成分的句子.其构成为"引导词+主语+谓语+其它",其语序是陈述句语序.引导宾语从句的连接词很多,多有实在意义,称为有意连词；that也可以引导宾语从句,但本身没有实在意义,称为无意连词.
1.that引导的宾语从句可以作动词、形容词等的宾语.主句中常见的谓语动词有say, know, hear, see, hope, think, believe, write, tell等.系动词加形容词afraid, worried, sure等后,也可用that引导的宾语从句.
如：I hope that he will come back soon. 我希望他能快点回来.
2.在由that引导的宾语从句中,由于连词that只起引导功能,无具体意义,不作句子成分, 因此在口语或非正式文体中常可省略,省略之后不影响原句性质和意义.
3.由that引导的宾语从句中的时态,通常分三种情况：若主句为一般现在时或一般将来时,宾语从句可根据具体情况选用时态；若主句是过去时,从句一般用相应的过去时态；若从句表示的是客观真理、名言、自然现象等,从句时态不受主句限制.
4.主句若是I/We think (believe, guess, suppose, imagine...)时,后面的宾语从句若要表示否定概念时,一般应将否定词not 转移到主句的谓语中.
如：I don't think (that) you are right. 我认为你不对.
5.含that宾语从句的复合句在变成反意疑问句时,如果主句的谓语动词为think,believe, guess, suppose, imagine等且主语是第一人称时,附加疑问部分要由从句决定；反之,附加疑问部分由主句决定.
如：I don't think that he can answer this question, can he?我认为他答不出这个问题,不是吗?
定语从句：
定语从句（Attributive Clauses）在句中做定语,修饰一个名词或代词,被修饰的名词,词组或代词即先行词.定语从句通常出现在先行词之后,由关系词（关系代词或关系副词）引出.
关系代词有：who, whom, whose, that, which等.
关系副词有：when, where, why等.
I like the music for the very reason that(for which) he dislike it. 我出于某种原因喜欢这种音乐,而他恰恰与我相反. .