1、选择性必修三Unit 2Discovering useful structuresThe infinitive of the verb used as the subjectHealthy 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 i
2、s never easy.2.It took the surgeon three hours to finish my mothers ling surgery.3.To join the peoples 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
3、 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 headach
4、e for me.（作主语）练习：1.When and where （vote）hasnt been decided.2.（何时装修）the house hasnt been decidedto 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。Its 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
5、 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 do2.It is+adj.+(of sb)to do3.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,exci
6、ting,interesting,surprising等。1.It isadj.(for sb.)to do sth.sb.是to do sth.的逻辑主语 It is necessary for you to change your job.Its 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 isadj.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
7、silly of you to give up such a good chance！Its very kind of you to say so.It was rude of the boy to jump the queue!It is necessary _ young students to learn aforeign 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
8、 night.forofof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 life4.It takes/took sb some time to do
9、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：动词动词-ing-ing形式和不定式作主语形式和不定式作主语,都是说明一个内都是说明一个内容。容。不定式通常不定式通常表示一个将来的、具体的内容表示一个将来的、具体的内容;但是但是,而动词而动词-ing-ing形式则表示一种形式则表示一种经常性的、习经常性的、习惯的或抽象的惯的或抽
10、象的概念。概念。To look after children is her job today.她她今天的今天的工作是看孩子。工作是看孩子。Looking after children is her work.她的工作是照顾孩子。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，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可以在不定式前加一个由 for/of for/of 引起的短语引起的短语,构成构成_。2.不定式作主语时,可以用it作_.4.It is+adj+for sb to do 5.It is+adj+of sb to do(adj:kind,good,ni
11、ce,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(adj.:easy,difficult,comfortable,pleasant,light,dangerous，tiresome,interesting,heavy,fit)单句语法填空（1）Sometimes its better （remain）silent.（2）Although is a hard task to protect our envi
12、ronment，we cant help but go ahead.（3）（control）the air pollution is necessary.（4）It was foolish him to endanger his life in that way.（5）Dont 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 dont
13、 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 Its 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 ad
14、d 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 youIt will take the nutrition specialist an hour to make
15、a balanced diet for you.3.useful/turn to/fitness consultant/for adviceIt is useful to turn to the fitness consultant foradvice.n.专家n.顾问4.illegal/dangerous/take drugs5.harmful/skip breakfast/oftenIt is illegal and dangerous to take drugs.It is harmful to skip breakfast often.n.毒品，药品v.跳过Complete the c
16、onversations with the correct forms of the phrases in the box.1.A:Hello,doctor.I want to lose weight,but I just cant seem to do it.What can you do to help me?B:Well,first,its necessary to _ what you eat.Cut out all fatty food and sugary drinks,and eat more fruit and vegetables.be in control ofbegin
17、with,be in control of,make a choice,decide on,make up ones mind2.A:I really need to _ a way to exercise more.I could use a fitness app,but my phones full.B:So delete a few files.Im sure the app doesnt take up much space.3.A:Before exercising,always do a few warm-ups to _.B:I know.But then I always f
18、eel too tired to continue!decide onbegin withbegin with,be in control of,make a choice,decide on,make up ones mind4.A:Should I go for the pizza or the fried chicken?I hate _ like these.You know whatIm going to eat both!B:Wow!Dont eat too much junk food-youll get fat,Ive actually _ to go on a diet,so Ill just stick to the fruit salad.making/to make a choicemade up my mindbegin with,be in control of,make a choice,decide on,make up ones mind
