Unit 1 Discover Useful Structures 语法学案-2021-2022学年高中英语人教版（2019）选择性必修第三册

Unit 1 Art

 Discover useful structures

课型：新授课     课时：2课时

班级:______姓名:________小组:_______

【学习目标】

Teaching Objectives：

1. Students will master the correct forms and functions of the infinitives.
2. Students will use the infinitives as predicative and subject correctly.

【了解感知】

不定式作表语

一．结构

am/is/are/was/were + 不定式

The purpose of education is to develop a fine personality in children.

二.功能

（1）表示目的

The next step is to understand exactly what conveys in the contemporary painting.

（2）表示事态发展的结果、预期的结果及预言

You must speak out, if we are to remain friends.

We believe man is to live a better life in the future.  

（3）用于第一人称疑问句，表示征求意见

What am I to do if I can’t gain entry to the final?

（4）用于被动语态，相当于should，具有情态意义

These books of great value are not to be sold.

（5）表示“安排、命令、决定、劝告、意愿、禁止”等

I am to set out for China next week. 下周我要动身到中国去。（安排）

You are to have a face-to-face talk with them. 你应该和他们当面谈一谈。（劝告）

Children are not to smoke. 儿童不准吸烟。（禁止）

三．动词不定式作表语的两种特殊用法

（1）不定式短语to let，to blame，to seek 等常用主动形式表示被动含义

The house is to let.

Who is to blame for the population decline of the tigers in that area?

The reason for global warming is not far to seek. 全球变暖的原因不难找到。

（2）当主语部分含有动词 do 的某种形式时，作表语的不定式可省略to

Anything we can do is guarantee it will be delivered on time.

In the evening the only thing he did was read on the blog.

四．总结

1. 句子主语是不定式时，系动词后可接不定式作表语，解释主语描述的行为或说明该行为带来的结果。

2. 不定式作表语时，能担当句子主语的名词有限，多用于表示某种情形或状况：advice, aim, custom, business, desire, difficulty, duty, experience, habit, happiness, hope, idea, intention, job, method, plan, principle, problem, purpose, reason, risk, role, task, thing, wish等。根据需要，有时不定式前可添加疑问代词或疑问副词，what, who, how, when, where等。

    My ambition is to become a scientist.

    His habit is to get up early.

    The problem was how to begin.

3. 当主语含定语从句且其先行词为代词all或形容词最高级the least, the most时：+系动词+不定式作句子的表语。

   All he wanted was to be left alone.

   The least I can expect is to have this day all to myself.

4. 当不定式作表语时，句子主语可以使what引导的主语从句。

   What I want to do now is (to) have a rest.

 

不定式作主语

读下列句子，体会动词不定式的用法。

To see is to believe. 百闻不如一见。

It is interesting to play with snow in winter.  冬季里玩雪是很有趣的。

It’s important for human beings to keep the balance of nature.保持自然平衡对人类来说很重要。

不定式是非谓语动词的一种，没有____________的变化，在句中可以作____________(有名词和代词的作用)，通常表示____________、____________行为。

一、用法

不定式位于句首

To study English well is not easy.

学好英语不容易。

it作形式主语，把不定式(短语)置于句末。

为了避免头重脚轻，可用it作形式主语，把不定式(真正主语)放到句子后面。

It would be a great honor for me to invite you to come to China.

邀请你来中国对我来说是一件非常荣幸的事。

As we all know，it is good for your health to stop smoking.

众所周知，戒烟益于健康。

二、动名词和不定式作主语的区别

一般来说，不定式作主语表示一次性的、具体的动作，而动名词作主语表示一种抽象的和泛指的动作。

To lie is wrong.

说谎是错误的。(对于说谎者是谁，说话人心中是有所指的)

Swimming is good exercise.

游泳是一项很好的锻炼。(指游泳这项运动)

巩固练习：

①It takes about ten minutes                              .