Unit2 Healthy Lifestyle不定式做主语课件（共21张）选择性必修第三册

(共21张PPT)
选择性必修三
Unit 2
Discovering useful structures
The infinitive of the verb used as the subject
动词不定式作主语
Healthy Lifestyle
Focus on
基本用法
不定式作主语
一、通常用法
二、*it作形式主语的用法
*it作形式主语时的三种情况
三、“疑问词+动词不定式”作主语
不定式作主语基本用法：
一. 动词不定式作主语，位于句首，谓语动词用单数。
1. To know yourself is difficult.
了解自己是很难的。
2. To love and to be loved is the greatest happiness one can get.
爱与被爱是一个人能获得的最大幸福。
3. To look after these naughty boys is really difficult.
照看这些淘气的男孩真的很难。
4. To save money now seems impossible.
现在存钱好像不可能。
不定式作主语通常位于句首，表示具体的、某一次的或将来的动作，谓语动词用单数。
1.不定式作主语通常表示一个将来的、具体的内容;
而动词-ing形式则表示一种经常性的、习惯的或抽象的概念。
To look after children is her job today.
她今天的工作是看孩子。
Looking after children is her work.
她的工作是照顾孩子。
不定式作主语和动词-ing形式作主语的区别：
1. To teach you the uses of the infinitive is my job today. (表具体行为) 教你们不定式的用法是我今天的工作。
2. Teaching is my job. (经常性行为)
教学是我的工作。
2. 如果主语用不定式，表语和宾语也用不定式；主语用动名词，表语和宾语也用动名词，这在英语中称为对称性。
To see is to believe.＝Seeing is believing.
眼见为实。
2. It is better to stay home than to go out.
待在家里比出去要好。
非谓语动词做主语：非谓语动词中的动词不定式和动词-ing形式作主语，一般谓语动词用单数。如果两个或两个以上的非谓语动词作并列主语，并且指两个或两个以上的动作时，谓语动词用复数。
Eating healthy food and taking exercise are very important.
吃健康的食物和锻炼是非常重要的。
特别提示：当两个或两个以上的非谓语动词表示同一概念时，谓语动词通常用单数。
To love and to be loved is the happiest thing.
爱与被爱是最幸福的事。
early to go to bed and early to rise （ make ）a man healthy.
makes
[巧学活用1]——单句语法填空
①________ (finish) reading the book will take you two hours.
②________ (pay) a visit to the Forbidden City is my dream.
③To improve people's lives and to speed up socialist construction _____ (be) two important tasks today.
④________ (stay) up too late is a bad habit for our health.
To finish
To pay
are
Staying
2. 当主语较长，谓语较短时，常用it作形式主语放在句首，而将真正的主语—不定式放到谓语的后面。
To work out the problem is not easy.
=It’s not easy to work out the problem.
To play with snow in winter is interesting .
=It is interesting to play with snow in winter.
To finish the building in a month is difficult.
=It is difficult to finish the building in a month.
考点：it 作形式主语常见的句型
1. It is+形容词+for/of sb +to do sth
It is easy me to learn how to drive.
It is clever you to apply for the position.
一般规律：
若形容词 ”人的性格、品质”, 用of;如good，kind，nice，foolish，polite，considerate，careless等。
若形容词“描述事或物的特征”, 用for;如：easy ,difficult, comfortable, pleasant, dangerous等等
for
of
It is stupid _______them to quarrel about this question.
It is easy _______ me to learn how to drive.
It is impolite ______ him to say so.
It is important _______ us to express our opinions.
It is clever ______ him to leave that company.
Exercises
of
for
for
of
of
2、接名词作表语：It is +n.+ to do sth.
It must be great fun to fly to the moon in a spaceship.
乘宇宙飞船飞往月球一定很有趣。
It is a pity for you to miss such a wonderful film.
你错过了这么好的电影，真可惜。
3. it作形式主语时，还常用于
“It takes sb. some time/money to do sth.” 句型中。
It took me more than an hour to do my homework yesterday evening.
昨天晚上我做作业用了一个多小时。
It will take us a lot of money to buy that house.
买那套房子要花费我们很多钱。
做某事花费某人多长时间(钱)
It seems(appears)+形容词+to do
It seemed impossible to save money.
4. it作形式主语时，还常用于
“It seems(appears)+形容词+to do句型中。
It seems necessary to mark a plan for this course of study. 制定学习这门课程的计划是必要的。
[巧学活用2]——单句语法填空
①[2022·新高考卷Ⅰ应用文]It is my pleasure ________ (invite) you to our English show “Talk and Talk” which will be conducted at 6 a．m. this Friday.
②It is good manners for the young ________ (give) their seats to the old.
③It is my ambition ________ (make) sure that the disabled people have access to all public buildings.
④It is no use ________ (argue) with him, for he is so stubborn.
to invite
to give
to make
arguing
不定式作主语，有时根据表达的需要，可以在添加疑问代词或副词，
疑问代词：who，whom，what，which
疑问副词：when，where，how
whether
E.g.
How to break the bad habit is the question.
Where to go hasn't been discussed.
It has not been decided whether to fly to Paris.
3.”疑问词+to do”作主语
[巧学活用3]——单句语法填空
①How ________ (cure) this kind of illness is still unknown.
②Whether ________ (do) it or not has not been decided.
③How ________ (deal) with this case hasn't been known yet.
to cure
to do
to deal
I.Choose the best answer.
1、It’s our duty ______ the room every day.
A. to clean B. cleaned
C. clean D. cleans
2、It’s hard for us _______ English well.
A. learn B. learns C. to learn D. learning
3、It’s very nice ___ you to get me two tickets ____ the World Cup.
A. for, of B. of, for C. to, for D. of, to
1. It is very helpful for all of us ________(help) a good knowledge of history.
2. It’s necessary for you ________ (lock) the car when you do not use it.
3. Afraid of ___________ (bite) by snakes, the boy was afraid ________ (touch) them.
4. ________(get) there by bike will take us half an hour.
Ⅱ. Practice
to help
to lock
being bitten
to touch
To get
Ⅲ. Translation.
1. 早起是必要的。
2. 对我们来说，完成这项工作很困难。
3. 如何控制水污染是一个大问题。
4. 步行去那儿要花费我们很长时间。
It’s difficult for us to finish the work.
How to control the water pollution is a big problem.
It will take us a long time to walk there.
To get up early is necessary.
2. 完成课时作业（六）
Homework:
1. 完成优化探究P42、43页
Thanks