资源简介

(共14张PPT)
Section Ⅲ　Learning About Language
UNIT 2 HEALTHY LIFESTYLE
动词不定式作主语
观察下面的句子，体会黑体词的用法。
①However，during this period, it can be easy for some of them to form bad habits.
②To prevent harmful habits like these from dominating a teenager's life is essential.
③To change bad habits is never easy.
④After all, it is not easy to break bad habits.
[自我归纳]
(1)以上句子中的动词不定式都作 。
(2)句①和句④中的it作 ，真正的主语是后面的 。
主语
形式主语
动词不定式
1．动词不定式作主语时，谓语动词常用单数。
To make up for lost time is not possible.
要弥补失去的时光是不可能的。
To see is to believe.
眼见为实。
2．为了避免句子头重脚轻，常用it作形式主语，放在句首，而把真正的主语——动词不定式置于句末，特别是不定式短语较长时。
To learn English well is not easy.
＝ It's not easy to learn English well.
学好英语不容易。
3．用it作形式主语，把真正的主语不定式后置，常用于下列句式中：
(1) It＋be＋名词＋to do
It's our duty to take good care of the old.
照顾老人是我们的责任。
(2) It takes sb. ＋ some time ＋to do
How long did it take you to finish the work
你花了多长时间完成这项工作？
(3) It＋be＋形容词＋for sb.＋to do
It is difficult for us to finish writing the composition in a quarter of an hour.
我们很难在一刻钟内写完这篇作文。
(4) It＋be＋形容词＋of sb.＋to do
It's careless of you to make so many mistakes.
你太粗心了，犯了这么多错误。
[注意]　①for sb. 的结构常用于表示事物的特征、特点，句中的形容词通常表示客观的情况，如easy, hard, difficult, interesting, impossible等。
It's necessary for you to lock the car when you do not use it.
当你不用车的时候，锁车是有必要的。
②of sb.的结构一般用表示人物的性格、品德、主观感情或态度的形容词，如good, kind, nice, clever, foolish, right等。
It was silly of us to believe him.
我们真愚蠢，竟然相信了他。
(5)It seems/appears＋形容词＋to do
It seemed impossible to save money.
省钱似乎是不可能的。
4．“疑问词＋不定式短语”结构作主语可置于句首。
How to learn English well is important.
如何学好英语很重要。
Where to put the bikes is being discussed.
把自行车放哪儿的问题正在讨论当中。
5．动名词与动词不定式作主语的区别：
(1)动名词作主语通常表示泛指或抽象动作；而动词不定式作主语通常表示特指或具体动作。有时这种区别并不严格，但要注意，主语和表语要用同一种形式，平行结构中也要用同一种形式。
Smoking is not good for health.
吸烟有害健康。
It is not good for you to smoke.
抽烟对你身体不好。
To see is to believe.＝Seeing is believing.
眼见为实。
Fishing is his hobby, and collecting stamps also gives him great pleasure.
钓鱼是他的爱好，集邮也给他带来很多乐趣。
(2)动名词作主语时，通常用以表示已知的事或经验；而动词不定式作主语通常用来表示未完成的事或目的。
Climbing mountains is interesting.
爬山很有趣。
To finish the task will take a long time.
要完成这项任务将要花费很长时间。
(3)常用动名词作主语的句型有“It's no good/use/fun doing sth.”“It's (a) waste of time doing sth.”等。
It is no good arguing with him. He never listens to others.
和他争论没好处，他从不听别人的。
Ⅰ.单句语法填空
1．It is important for her (prepare) for the examination.
2．It's very hard him to study two languages.
3．It's very nice you to help me.
4. (nod) your head means saying “yes” in China.
5. (finish) the work in a week is impossible.
6．It's our duty (keep) our environment clean and tidy.
to prepare
for
of
Nodding
To finish
to keep
Ⅱ.完成句子
1．尽力处理这些问题是我们的责任。
deal with these problems. (duty)
2．班主任说有必要和他母亲谈一谈。
The head teacher said . (necessary)
3．建造这座立交桥将花费工人们一年多的时间。
It will the flyover.(take)
It is our duty to try our best to
it was necessary to talk with his mother
take the workers over a year to build
4．去哪里借这些钱还不得而知。
this sum of money is not known.(borrow)
5．爱与被爱是一个人所能寻找的最大的幸福。
is the greatest happiness one can seek. (love)
Where to borrow
To love and to be loved

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