三大从句与动词不定式的转换

一、定语从句与不定式的转换

1.“介词+关系代词”引导的定语从句，主句与从句主语一致时，可转换为“介词+关系代词+不定式”结构。命题方向主要为考查“介词+关系词”的选择。

例1 The farmers use wood to build a house ______ to store grains all the year round.

A. with which B. to which

C. for which D. on which

解析：此题可还原为一个“介词+关系代词”引导的定语从句：The farmers use wood to build a house with which they can store grains all the year round.因主句与从句主语一致，把定语从句转换为“介词+关系代词+不定式”结构，即“with which to store”。答案为A。

例2 Frank’s dream was to have his own shop ______ to produce the workings of his own hands.

A. that B. in which C. by which D. how

解析：此题可还原为一个“介词+关系代词”引导的定语从句：Frank’s dream was to have his own shop in which he could produce the workings of his own hands. 因主句与从句主语一致，把定语从句转换为“介词+关系代词+不定式”结构，即“in which to produce”。答案为B。

2.定语从句转换为不定式作定语，表示将来。命题方向主要为考查不定式作定语表将来意义。

例3 The play ______ next month aims mainly to reflect the local culture.

A. produced B. being produced

C. to be produced D. having been produced

解析：此题可还原为一个定语从句：The play which will be produced next month aims mainly to reflect the local culture.因不定式的一般式可以作定语，表将来意义，可把表示将来被动的定语从句“which will be produced next month” 改为不定式的被动形式“to be produced next month”。答案为C。

例4 The chairman insists that there be a meeting ______ within the shortest possible time.

A. to hold B. to be held

C. to have been held D. to be holding

解析：此题可还原为一个定语从句：The chairman insists that there be a meeting which will be held within the shortest possible time.因不定式的一般式作定语可表示将来，可把表示将来被动的定语从句which will be held 改为不定式的被动形式to be held。答案为B。

二、名词性从句与不定式的转换

1.宾语从句与不定式的转换：当疑问词引导的宾语从句的主语与主句主语一致时，可转换为“疑问词+不定式”结构。命题方向主要为考查不定式短语。

例5 It is said in Australia there is more land than the government knows ______.

A. it what to do with B. what to do it with

C. what to do with it D. to do what with it

解析：此题可还原为一个宾语从句：...the government knows what it will do with it.前一个it 指the government，宾语从句的主语与主句主语一致时，可转换为“疑问词+不定式”结构，即“what to do with it”。答案为C。

2.由it作形式主语的主语从句与不定式的转换：

（1）句型“It+be+said / reported / believed / thought / supposed that sb. / sth. +谓语”可转换为“sb. / sth.+be+said / reported / believed / thought / supposed +不定式”。命题方向主要为考查不定式的时态和语态。

例6 ―Is Bob still performing？

―I’m afraid not. He is said ______ the stage already as he has become an official.

A. to have left B. to leave

C. to have been left D. to be left

解析：此题可把“He is said ______ the stage already as he has become an official”还原为“It is said that he has left the stage already ...”。题干中的句型为“sb. is said +不定式”，already 暗示完成，所以用不定式的完成式，主语和谓语是主动关系，即“He is said to have left ...”。答案为A。

例7 Bell is believed ______ the first telephone in 1876.

A. to invent B. to have invented

C. that it is D. to have been invented

解析：此题可把“Bell is believed ______ the first telephone in 1876”还原为“It is believed that Bell invented the first telephone in 1876”。题干中的句型为“sb. is believed+不定式”，又因有具体的过去时间，所以用不定式的一般式，主语和谓语是主动关系，即“Bell is believed to invent ...。”答案为A。

（2）“It seems / seemed that sb. / sth. +谓语”转换为“sb. / sth. seems / seemed +不定式”结构。命题方向主要为考查不定式的时态和语态。

例8 Here we found little snow，as most of it seemed ______ off the mountain.

A. to have been blown B. to have blown

C. to be blown D. to be blowing

解析：此题可把“as most of it seemed ______ off the mountain”还原为“as it seemed that most of it had been blown off the mountain”。题干中的句型为“sth. seemed+不定式”，here we found little snow暗示动作已完成，且主语和谓语是被动关系，即“as most of it seemed to have been blown ...”。答案为A。

三、状语从句与不定式的转换

状语从句可改为不定式作状语，表示目的、结果或方式。命题方向主要为考查不定式作状语。

1. so ...that引导的结果状语从句可以转换成不定式的简单句。

（1）当主句和从句的主语一致，that从句是肯定句时，可用enough to do sth.来转换;当that从句是否定句时，可以用too ... to来替换。

He was so clever that he can understand what I siad.

He was clever enough to understand what I siad.

The girl is so young that she can’t dress herself.

The girl is too young to dress herself.

（2）当主句和从句的主语不一致，且that从句是肯定句时，可以用enough for sb. to do sth.来替换;当that从句是否定句时，用too ... for sb. to do sth.替换so ... that时，注意不定式的宾语要省略。

The question is so easy that I can work it out.

The question is easy enough for me to work out.

The bag is so heavy that she can’t move it.

The bag is too heavy for her to move.

2. so that/in order that引导的目的状语从句与主句主语一致时，可改为to do 或“in order to/so as to do ...”结构，表目的。

例9 All these gifts must be mailed immediately ______ in time for Christmas.

A. in order to have received B. in order to receive

C. so as to be received D. so as to be receiving

解析：此题可把“All these gifts must be mailed immediately ______ in time for Christmas”改为 so that/in order that引导的目的状语从句：All these gifts must be mailed immediately so that/in order that they can be received in time for Christmas。主句和从句的主语一致，可把从句改为不定式表目的，且主语和谓语是被动关系，即“to be received/in order to be received /so as to be received”。答案为C。

3. as if 引导的方式状语从句与主句主语一致时，可改为不定式作状语。

例10 The man we followed suddenly stopped and looked as if ______ whether he was going in the right direction.

A. seeing B. having seen

C. to see D. to have seen

解析：此题可把“looked as if ______ whether he was going in the right direction”改为as if 引导的方式状语从句：looked as if he wanted to see whether he was going in the right direction.主句和从句的主语一致，可把从句改为不定式作状语 ，即“as if to see”。答案为C。