1、UNIT 2 HEALTHY LIFESTYLEDiscover Useful Structureslead in 1. To change bad habits is never easy. 2. It took the surgeon three hours to finish my mothers lung 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 neighb
2、ours with loud music last night.The infinitive in each sentence functions as the subject of the sentence.动词不定式作主语动词不定式直接放在句首作主语1. To see is to believe.2. To say is one thing and to do is another.从位置上看，动词不定式作主语，通常放在句首。当句子主语和表语都是非谓语时，通常要保持一致，例如：To see is to believe. = Seeing is believing.动词不定式作主语于首常出现
3、在正式文体中。单个不定式作主语,谓语动词用_形式。To get enough protein each day is beneficial to our health. 每天摄取足够的蛋白质对我们的健康有益。单数动词不定式作主语 2.为了保持句子平衡，用It作形式主语，放在句首，把真正的主语动词不定式置于句后句首用形式主语 it 代替1.It is not right for your parents to dominate your life.Its hard for me to answer the question.句子的表语都是_形容词it + be + adj + (逻辑主语逻辑主语
4、) + to do sth句首用形式主语 it 代替It +be+ 名词 +to do sth.做某事是1. Its our duty to do that.2. Its a mistake not to help them. It takes sb. some time to do sth.做某事花费某人一些时间。It will take us a long time to walk there.It took me more than an hour to do my homework yesterday evening.动词不定式作主语3. 和疑问词构成短语作主语和疑问词构成短语作主语
5、1. How to use the phone is a question. 2. Where to put the cars is being discussed. 3. When and where to have a barbecue has not been decided.可用于该结构的疑问词疑问代词:who,whom,what,which疑问副词:when,where,how常接该结构的动词know, see, decide , tell , ask, consider, explain, learn, wonder该结构的句法功能:主语、宾语和表语The question is
6、when to start developing such a vaccine.问题是何时开始研制这种疫苗。(作表语)“疑问词+不定式”结构相当于一个由疑问词引导的名词性从句。How to use the computer is a question. = _How we can use the computer is a question.不定式短语作独立成分 一些不定式短语可用作独立成分,通常位于句首,有时位于句中或句末,要用逗号同其他句子成分隔开。To tell the truth, I dont like the gifted actress in the movie.常用短语to s
7、um up 总而言之 to be brief 简言之 to be exact 确切地说 to be frank 坦白地说 to be honest 说老实话 Practice It is wrong for you_(skip)breakfast. Although_is a hard task to protect our environment, we cant help but go ahead. It took the doctor about half an hour_ (examine) the eyes of thebaby. It was foolish_ him to endanger his life in that way. It is difficult_him to live on such a small salary.to skip ;it;to examine;of ;for谢谢观看2 0 2 0
