非谓语：动词不定式（to do）作主语，表语及定语知识点综合讲解及习题专练（附答案）

一. 动词不定式（to do）作主语：

（一）不定式（to do）短语可放在句首作动词be，seem，appear等词的主语。

  e.g. To study the structure of the plant is necessary for every student learning agriculture.

          To see is to believe.

          To become a good teacher was my hope.

（二）当动词不定式（to do）作主语时，为了平衡句子结构，经常把代词it放在句首作形式主语，而把真正的主语（动词不定式）放在句末。

(1) It is + difficult/ hard / easy / important / necessary + for sb. to do

sth. 干某事对某人来说是怎么样的。

(2) It is + kind / good / nice / clever of sb. to do sth. 某人做某事是怎么样的。

e.g. It is useful for you to learn English well.

        It’s too hard to understand spoken English.

        It is important for us to protect the environment.

        It’s very kind of you to help me.

二. 动词不定式（to do）作表语：

（一）动词不定式（to do）作表语，通常说明或解释主语的内容，也可表示将来的动作。

  e.g. Our purpose is to finish the job in three weeks.

          The duties of a postman are to deliver letters and newspapers.

三. 动词不定式（to do）作定语：

（一）动词不定式（to do）常用在the first，the second，the last，the only等短语后面作定语。

  e.g. He was the first to arrive.

          She was the only one to survive the crash.

（二）动词不定式（to do）常放在某些名词或者代词后面作定语：动词不定式（to do）作定语与被修饰的中心词之间常表现为主谓关系，动宾关系，同位关系或者动状关系等；常见动词包括

ability能力；

failure失败；

refusal拒绝；

agreement同意；

intention打算；

ambition雄心；

hope希望；

resolution决定；

tendency倾向；

attempt意图；

plan计划；

threat威胁；

promise诺言；

willingness愿意；

decision决定；

wish希望；

determination决心等

  e.g. I’m not sure which restaurants to eat out.

          We are in need of nurses to look after the children.

            He gave me a week to make up my mind.

            Their decision to give up the experiment surprised us.

（三）如果作定语的不定式（to do）为不及物动词，后面需加介词。

e.g. They have no happiness to speak of.

        Children use pencils to write with.

（四）“介词 + which + to do”作定语，which代表前面的中心词。

e.g. You have a number of topics from which to choose.

        I believe that is a proper standard by which to judge people.

四. 精品专练及参考答案：

（一）精品专练：

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