(
课件网) 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 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 不定式作主语基本用法： 一. 动词不定式作主语，位于句首，谓语动词用单数。 1. To know yourself is difficult. 了解自己是很难的。 2. To love and to be loved is the greatest happiness one can get. 爱与被爱是一个人能获得的最大幸福。 3. To look after these naughty boys is really difficult. 照看这些淘气的男孩真的很难。 4. To save money now seems impossible. 现在存钱好像不可能。 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。 1.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形式作主语的区别： 1. To teach you the uses of the infinitive is my job today. (表具体行为) 教你们不定式的用法是我今天的工作。 2. Teaching is my job. (经常性行为) 教学是我的工作。 2. 如果主语用不定式，表语和宾语也用不定式；主语用动名词，表语和宾语也用动名词，这在英语中称为对称性。 To see is to believe.＝Seeing is believing. 眼见为实。 2. It is better to stay home than to go out. 待在家里比出去要好。 非谓语动词做主语：非谓语动词中的动词不定式和动词-ing形式作主语，一般谓语动词用单数。如果两个或两个以上的非谓语动词作并列主语，并且指两个或两个以上的动作时，谓语动词用复数。 Eating healthy food and taking exercise are very important. 吃健康的食物和锻炼是非常重要的。 特别提示：当两个或两个以上的非谓语动词表示同一概念时，谓语动词通常用单数。 To love and to be loved is the happiest thing. 爱与被爱是最幸福的事。 early to go to bed and early to rise （ make ）a man healthy. makes [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 It is easy me to learn how to drive. It is clever you to apply for the position. 一般规律： 若形容词 ”人的性格、品质”, 用of;如good，kind，nice，foolish，polite，considerate，careless等。 若形容词“描述事或物的特征”, 用for;如：easy ,difficult, comfortable, pleasant, dangerous等等 for of It is stupid _____them to quarrel about this ... ...
