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

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 todays 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 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 of 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. 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+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, 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.Examination1. _ 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 habit 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 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