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二、不定式 1.不定式做主语 （1）做形式主语的代词： 不定式做主语，通常用it充当形式主语，把做主语的不定式短语后置。如： It took me only five minutes to finish the job. To be frank， it is a great relief to have the task fulfilled in so short a time. （
二、不定式
1.不定式做主语
（1）做形式主语的代词：
不定式做主语，通常用it充当形式主语，把做主语的不定式短语后置。如：
It took me only five minutes to finish the job.
To be frank， it is a great relief to have the task fulfilled in so short a time.
（2）引导逻辑主语的介词：
不定式的逻辑主语一般由介词for引导，但下列表示人的性格行为特征的形容词做表语时，不定式的逻辑主语则由of引导：
absurd， bold， brave， courageous， careful， careless， clever， wise， foolish， silly， stupid， good， nice， kind， thoughtful， considerate， greedy， generous， honest， modest， polite， rude， cruel， selfish， lazy， wicked， wrong.如：
Experts say walking is one of the best ways for a person to stay healthy.
It''s clever of you to have invented such a device.
（3）不定式做主语补足语：
掌握常用不定式做主语补足语的句型。注意不定式表示的动作发生的时间，并采用相应形式。如：
said
reported
thought
be to do sth.
believed
known
supposed
Byron is said to have lived on vinegar and potatoes.
The bank is reported in the local newspaper to have been robbed in broad daylight yesterday.
2.不定式做宾语
（1）必须接不定式做宾语的动词：
掌握要求接不定式做宾语的动词：
agree， afford， aim， arrange， appear， ask， attempt， choose， claim， decide， desire， determine， expect， fail， guarantee， hope， endeavor， intend， long， mean， manage， offer， ought， plan， pledge， pretend， prepare， promise， proceed， prove， resolve， refuse， request， swear， tend， try， venture， wait， wish.如：
Even though the children pretended to be asleep， the nurses were not deceived when they came into the room.
注意：
1）有的动词要求特殊疑问词+不定式做宾语，这类动词有：
consider， discover， explain， forget， guess， know， learn， observe， remember， see， tell， understand， wonder，如：
While still a young boy， Bizet knew how to play the piano well and as he grew older， he wrote operas， the most famous of which is Carmen.
2）如果该特殊疑问词在不定式中做介词宾语，介词往往置于该特殊疑问词的前面。如：
The professor can hardly find sufficient grounds on which to base his argument in favor of the new theory.
Without facts， we cannot form worthwhile opinion for we need to have factual knowledge upon which to base our thinking.
（2）可以用不定式做宾语补足语（复合宾语）的动词：
下列动词可以用不定式做宾语补足语（复合宾语）：
advise， allow， ask， beg， cause， command， compel， enable， determine， encourage， expect， feel， find， force， hate， have， hear， help， inform， invite， let， like， make， mean， need， notice， notify， oblige， order， permit， persuade， remind， request， require， see， send， teach， tell， tempt， trouble， urge， want， warn， watch， wish.
注意：画线动词后面的不定式不带to.
如：
Because of the recent accidents， our parents forbid my brother and me to swim in the river unless someone agrees to watch over us.
3.不定式做定语
（1）被修饰的名词前有序数词、形容词最高级或next， last， only， not a， the， very等限定词时，该名词用不定式做定语。如：the first woman to set foot on the moon第一个登上月球的女性
（2）如果其动词要求不定式做宾语，相应的名词一般用不定式做定语。如：
tendency to do→tend to do， decision to do→decide to do This book is an attempt to help you use English and recognize how it is used.
（3）如果其形容词形式要求接不定式做补语，相应的名词一般用不定式做定语。如：
ambition to do“干……的雄心”→be ambitious to do“有雄心干……”
curiosity to do“对……的好奇心”→be curious to do“对……好奇”
ability to do“做……的能力”→able to do“有能力做……”
According to Darwin， random changes that enhance a species''ability to survive are naturally selected and passed on to succeeding generation.
（4）表示方式、原因、时间、机会、权利等名词用不定式做定语，这些名词包括：
way， method， reason， time， place， chance， occasion， opportunity， evidence， power， right， movement， drive （运动），effort等。如：
I worked so late in the office last night that I hardly had time to catch the last bus.
We appreciate your efforts to bring about a comprehensive solution to the existing problem.
（5）不定代词something， nothing， little， much， a lot习惯上用不定式做定语。如：
Though we have made great progress， there is still much to be improved.
4.不定式做状语
不定式做状语主要表示目的、程度、结果、方式。
（1）in order to（do）， so as to（do）结构引导目的状语，so as to不能置于句首。如：
To succeed in a scientific research project， one needs to be persistent .
I advise them to withdraw so as not to get involved.
（2）so…as to， such…as to， enough…to， too…to结构做程度状语。如：
The solution works only for couples who are self-employed， don''t have small children and get along well enough to spend most of their time together.
The vocabulary and grammatical differences between British and American English are so trivial and few as hardly to be noticed.
（3）不定式做结果状语只能出现在句子的末尾，表示不愉快的结果，有时用only加强语气。
常见的不定式动词有find， hear， see， be told， form， give， make， produce等。如：
Greatly agitated， I rushed to the apartment and tried the door， only to find it locked.
（4）not/never too…to， too…not to， but/only too…to， too ready/eager/apt/inclined to表示肯定意义。如：
I am only too pleased to hear from you further.能再听到你的消息，我太高兴了。
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