Unit 2 Discover useful structures 导学案-高中英语人教版（2019）选择性必修第三册.docx

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1、Learning objectives: By the end of this period, you will be able to1. master the usage of the infinitive as subject.2. distinguish infinitive as subject from V-ing as subject2. use the infinitives flexibly and authentically in real situation.Self-study一、 不定式直接作主语Observe:1. To clean the window is tod

2、ays job.2. To jump out of the window is dangerous.3. To finish the work before Friday is not so easy.Discovery: 以上句子中动词不定式（短语）在句中直接作_ (成分),谓语动词采用_ 形式。不定式做主语与动名词做主语的区别一般来说，不定式做主语，表示具体的、一次性的或将来的动作；动名词做主语，表示一般的、泛指的或习惯性的行为。但是在多数情况下无明显区别。如To see is to believe.=Seeing is believing.练习： _(teach) English is

3、my job. _(teach) you English this term is my job. To say is one thing and _(do) is another. To change bad habits _(be) never easy, even with many attempts. 二、 it 作形式主语，不定式作真正的主语Observe:1. It is interesting to play with snow in winter.2. Its important for us to keep the water clean.3. Its very kind o

4、f you to help me.4. It must be great fun to fly to the moon in a spaceship.5. It took me more than an hour to do my homework yesterday evening.6. It appears unlikely to come back in half an hour.Discovery: 1)以上5个句子中动词不定式在句中均作_成分。2) 句1的句式结构是It is + _ +to do sth.3) 句2的句式结构是It is + adj. + _ + to do sth

5、. 该形容词描述物，此类adj有easy, difficult, comfortable, pleasant, light, heavy, dangerous, interesting , fit等。4) 句3的句式结构是It is + adj. + _ + to do sth. 该形容词描述人，此类adj有kind, good, nice, wise, unwise, clever, silly, stupid, foolish, careless, rude, polite, naughty5) 句4的句式结构是It is + _ + to do sth.6) 句5的句式结构是 It _句

6、型。7) 句6的句式结构是 It seems/ appears + adj. + _.练习： It is possible _ (walk) or bike the entire 14 kilometers. She admits _ took her a while to come around to the opinion. It is a great fun _ him to leave for the other city to work. It seemed selfish _ him not to share his dictionary with others.三、 “特殊疑问词

7、+不定式”作主语Observe：1. How to use the computer is a question.2. Where to go has not been decided.3. When to start hasnt been decided yet.4. Whether to drive or take a taxi is still a question.Discovery: 1)上面4个句子的主语分别是_, _, _, _.2) 以上例句谓语动词都是用的_ 形式。3) 通过以上可发现，动词不定式可与疑问词what, who, which, when, where, why,

8、 how 或者whether 等连用构成不定式短语作主语，谓语动词用第三人称单数形式。练习： Where and when _ (cast) a net is more important than how to cast a net. Whether to compete in the relay race _ (be) a decision that has to be made by our teacher. How the work should be finished is still a question.= How _ the work is still a question.E

9、xamination1. _ took us a long time to repair the house.2. It is foolish _ you to turn down the proposal(提议).3. It is important _ her to prepare for the examination.4. When you are in trouble, it is _ (help) to turn to your teacher.5. To form a good habit _ (be) difficult while to fall into a bad hab

10、it is easy.6. Whether _ (hold) a party this weekend hasnt been known yet.Homework & Practice1. It is difficult _ (figure) out a global population of polar bears.2. The implication of these results is that to gain the greatest health benefits from exercise, it may be wise _ (skip) eating first.3.Then

11、 we will know how important it is _ us to have meaning in our life.4. Coming out of this experience, I realize it is OK _ (be) different from others.5. Exercise energizes you, so _is more difficult to relax and have a peaceful sleep when you are very excited.6. It seemed a pity _ (waste) so much time on the task without achieving our goal.3学科网（北京）股份有限公司