人教版（2019）选择性必修第三册Unit 2 Healthy Lifestyle不定式做主语课件 （22张ppt）

(共22张PPT)
选择性必修三
Unit 2
Discovering useful structures
The infinitive of the verb used as the subject
Healthy Lifestyle
单元语法自我探究
Look at the following sentences and pay attention to the italicized infinitives. Find more infinitives in the reading passage, and tell their meanings and functions.
1. To change bad habits is never easy.
2. It took the surgeon three hours to finish my mother’s ling surgery.
3.To join the people’s Liberation Army, it is required for men to shave off their beards.
4. It was not polite to disturb your neighbors with loud music last night.
主语
主语
主语
主语
动词不定式作主语常见的三种形式
1. 不定式作主语通常位于句首，表示具体的某次动作，谓语动词用单数。
To see is to believe.
To get up early is necessary.
To finish the building in a month is difficult.
2.疑问词 + 不定式 做主语
疑问代词：who，whom，what，which
疑问副词：when，where，how
How to use the computer is the question. （作主语）
When to start developing such a vaccine is the question. （作主语）
Where to find that young man is a headache for me. （作主语）
练习：
1.When and where 　　　　 　（vote） hasn’t been decided.
2.　 　 　　（何时装修） the house hasn’t been decided
to vote
When to decorate
3. 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。
It’s not easy to work out the problem.
= To work out the problem is not easy.
It is interesting to play with snow in winter.
It is terrible to see the ship sinking into the sea
不定式作主语，it 做形式主语的常见结构：
1.It is +adj.+(for sb) to do
2.It is +adj.+(of sb) to do
3.It is +n.+ to do sth( an honour, our duty, a pity, a shame)
4.It takes/took sb some time to do sth.
用于此句型的形容词一般是修饰做某件事的形容词有：easy, hard, difficult, possible, important, impossible, necessary, good, bad, exciting, interesting, surprising等。
1. It is＋adj. (＋for sb.) to do sth.
sb. 是to do sth.的逻辑主语
It is necessary for you to change your job.
It’s difficult for us to learn English well.
常见的此类形容词有： kind, nice, wise, silly, polite, impolite, friendly, foolish, clever等。
2. It is＋adj.＋of sb.＋to do sth.
形容词用来表示不定式的逻辑主语（sb.）的性质、特征或品德
It was silly of you to give up such a good chance！ It’s very kind of you to say so.
It was rude of the boy to jump the queue!
It is necessary ______ young students to learn a foreign language.
It was silly ______ you to give up such a good chance！
It was not polite ______ you to disturb(v. 打扰)your neighbours with loud music last night.
for
of
of
常见的名词有：pity, shame, pleasure, fun, joy等。
It is our duty to take care of you.
3. It is + n. + (for sb.) to do sth.
A: I heard that the new head master has too many things to do.
B: Yes. It will be a big challenge for him ________________________________(平衡工作和生活) .
to balance his work and personal life
4.It takes/took sb some time to do sth.
It takes me half an hour to do my housework.
昨天晚上我用了一个多小时完成作业。
It took me more than an hour to finish my homework yesterday evening.
不定式作主语和动词-ing形式作主语和动词的区别：
动词-ing形式和不定式作主语, 都是说明一个内容。
不定式通常表示一个将来的、具体的内容;
但是, 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。
3. 如果要说明不定式表示的动作是谁做的，
可以在不定式前加一个由 for/of 引起的短语,构成_______________。
2. 不定式作主语时,可以用it作_______________.
It is+adj+for sb to do ……
5. It is+adj+ of sb to do………
(adj: kind, good, nice, wise, unwise, clever, silly, stupid, foolish,
careless, rude, polite, naughty)
（修饰人品形容词）
（修饰物的形容词）
1.单个不定式作主语，谓语动词_____________
单数
形式主语
不定式的复合结构
语法总结
(adj.: easy ,difficult, comfortable, pleasant, light , dangerous， tiresome, interesting , heavy, fit)
单句语法填空
（1）Sometimes it’s better 　　　　 　（remain） silent.
（2）Although 　　　　 　 is a hard task to protect our environment，we can’t help but go ahead.
（3） 　　　 　 　（control） the air pollution is necessary.
（4）It was foolish 　　　　 　 him to endanger his life in that way.
（5）Don’t you think it is rude 　　　　 　 him to ask a lady her age
（6）It is difficult 　　　　 　 him to live on such a small salary.
to remain
it
To control/Controlling
of
of
for
完成句子
（7）I don’t think 　_____________________________　　　　　　　　　　 （你问……是不礼貌的） how long the interview will last.
（8） 　　　　　　　　　　　（保卫…… 是我们的职责） the country against its enemies.
（9） 　　　　　　　　　　　（ …… 花了我半个小时）to wash the clothes.
it is impolite of you to ask
It’s our duty to defend
It took me half an hour
Join the words to make full sentences, and then join the sentences to make a paragraph. You can add your own sentences if necessary to make your paragraph more meaningful.
1. important/ avoid/ passive cigarette smoking
It is important to avoid passive cigarette smoking.
n. 香烟
2. will take/ nutrition specialist/ a balanced diet menu/ make/ an hour/ for you
It will take the nutrition specialist an hour to
make a balanced diet for you.
3. useful/ turn to/ fitness consultant/ for advice
It is useful to turn to the fitness consultant for
advice.
n. 专家
n. 顾问
4. illegal/ dangerous /take drugs
5. harmful / skip breakfast / often
It is illegal and dangerous to take drugs.
It is harmful to skip breakfast often.
n. 毒品，药品
v. 跳过
Complete the conversations with the correct forms of the phrases in the box.
1. A: Hello, doctor. I want to lose weight, but I just can’t seem to do it. What can you do to help me
B: Well, first, it’s necessary to ______________ what you eat. Cut out all fatty food and sugary drinks, and eat more fruit and vegetables.
be in control of
begin with, be in control of, make a choice, decide on, make up one’s mind
2. A: I really need to __________ a way to exercise more. I could use a fitness app, but my phone’s full.
B: So delete a few files. I’m sure the app doesn’t take up much space.
3. A: Before exercising, always do a few warm-ups to ___________.
B: I know. But then I always feel too tired to continue!
decide on
begin with
begin with, be in control of, make a choice, decide on, make up one’s mind
4. A: Should I go for the pizza or the fried chicken I hate _____________________ like these. You know what—I’m going to eat both!
B: Wow! Don’t eat too much junk food-you’ll get fat, I’ve actually ___________________ to go on a diet, so I’ll just stick to the fruit salad.
making/to make a choice
made up my mind
begin with, be in control of, make a choice, decide on, make up one’s mind
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