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课件网) Unit 2 Healthy Lifestyle Period 2 Learning about language 动词不定式作主语 Infinitives as the subject Look at the following sentences and pay attention to the infinitives. Observe and Discover 1 To change bad habits is never easy. 2 It took the surgeon (n.外科医生) three hours to finish my mother’s lung surgery (n. 外科手术). subject 主语 句子结构分析： It takes sb some time to do sth = To do sth takes sb some time. (It 为形式主语，真正的主语to do) subject 主语 形式主语 3. To join the People’s Liberation (n. 解放) Army, it is required for men to shave off (剃掉) their beards(胡须). 正常语序： To shave off beards is required for men to join the People’s Liberation Army. subject 主语 subject 主语 目的状语 4 It was not polite to disturb(v. 打扰)your neighbours with loud music last night. 正常语序： To disturb your neighbours with loud music last night was not polite. It is +adj (for sb) to do sth subject 主语 subject 主语 It is never easy to change bad habits. Tip 1：将形式主语 _____ 置于句首，_____ 置于句末，可以 避免句子头重脚轻、结构失衡。 Change the sentence structures. it 动词不定式 Tip 2: 动词不定式作主语时，谓语动词常用_____。 To change bad habits is never easy. To help others gives a person satisfaction（满足）. To prevent harmful habits like these from dominating a teenager’s life is essential. Task 2: Observe and explore. 单数 Tip 3: 在 It + is/was + 形容词 + to do 的句式中, 当该形容词用以表示to do的特征时，使用 It is/was ＋ adj. ＋ ____ + sb. + to do；当该形容词用来表示不定式的逻辑主语(sb.)的性质、特征或品德时，使用 It is/was ＋ adj. ＋ ____ + sb. + to do。 for of 1. It isn’t right for us to stop half way. = To stop half way is not right. 2. It’s kind of you to think so much of us. = You are kind to think so much of us. It is +adj.+ for/of sb. to do sth. 1) It is ＋ adj. ＋for sb. to do sth. 此处的形容词用来修饰后面的动词不定式， 常用于表示事物的特征，用于此句型的形容词有：easy, hard, difficult, possible, important, impossible, necessary, good, bad, exciting, interesting, surprising等。 It is necessary for young students to learn a foreign language. 对年轻的学生来说，学习一门外语是必要的。 As we all know，it is good for you to keep exercising. 众所周知，坚持锻炼益于健康。 2) It is ＋ adj. ＋of sb. to do sth. 此处的形容词用来修饰sb，常用于表示事物的特征，用于此句型的形容词有：kind, nice,wise, silly, polite, impolite, friendly, foolish, clever等。 It was careless of him to make such a mistake. 出了这样的错误，他太粗心了。 It’s very kind of you to say so. 你这样说真是太好了。 It was rude of the boy to speak loudly in public! 那个男孩在公共场合大声说话真是太无礼了! Tip 4: 动词不定式也可用在 it+be+n.+to do sth的句型结构中，it 做 _____ ，正真的主语是_____ 。 Observe and Discover 1. It’s our duty to do that. 2. It’s a mistake not to help them. 3. It must be great fun to fly to the moon in a spaceship. 动词不定式 形式主语 Tip 5: 动词不定式充当 ，用在表示某人花多少钱或金钱做 ... ...
