Unit2 A Healthy Lifestyle 不定式做主语课件-2023-2024学年高中英语人教版（2019）选择性必修第三册

选择性必修三 Unit 2 Discovering useful structures The infinitive of the verb used as the subject 动词不定式作主语 Healthy Lifestyle 1 Focus on 基本用法 不定式作主语 一、通常用法 二、*it作形式主语的用法 *it作形式主语时的三种情况 三、“疑问词+动词不定式”作主语 1. 不定式作主语通常位于句首，表示具体的、某一次的或将来的动作，谓语动词用单数。 To see is to believe. To get up early is necessary. To finish the building in a month is difficult. 一【含义】 不定式作主语通常表示一个将来的、具体的内容; 而动词-ing形式则表示一种经常性的、习惯的或抽象的概念。 To look after children is her job today. 她今天的工作是看孩子。 Looking after children is her work. 她的工作是照顾孩子。 不定式作主语和动词-ing形式作主语和动词的区别： [巧学活用1]——单句语法填空 ①________ (finish) reading the book will take you two hours. ②________ (pay) a visit to the Forbidden City is my dream. ③To improve people's lives and to speed up socialist construction _____ (be) two important tasks today. ④________ (stay) up too late is a bad habit for our health. To finish To pay are Staying 2. 当主语较长，谓语较短时，常用it作形式主语放在句首，而将真正的主语—不定式放到谓语的后面。 To work out the problem is not easy. =It’s not easy to work out the problem. To play with snow in winter is interesting . =It is interesting to play with snow in winter. To finish the building in a month is difficult. =It is difficult to finish the building in a month. 考点：it 作形式主语常见的句型 1. It is+形容词+for/of sb +to do sth E.g. It is easy for me to learn how to drive. It is clever of you to apply for the position. 一般规律： 若形容词 ”描述人的属性，特征”, 用of; 若形容词“描述事或物的特征”, 用for; It is stupid _______them to quarrel about this question. It is easy _______ me to learn how to drive. It is impolite ______ him to say so. It is important _______ us to express our opinions. It is clever ______ him to leave that company. Exercises 2、接名词作表语：It is +n.+ to do sth. It must be great fun to fly to the moon in a spaceship. 乘宇宙飞船飞往月球一定很有趣。 It is a pity for you to miss such a wonderful film. 你错过了这么好的电影，真可惜。 3. it作形式主语时，还常用于 “It takes sb. some time/money to do sth.” 句型中。 It took me more than an hour to do my homework yesterday evening. 昨天晚上我做作业用了一个多小时。 It will t