03 选择性必修三 Unit 2 不定式做主语（语法精讲精练）-2023-2024学年高二英语下学期期末复习高效突破（人教版2019）

03 选择性必修三 Unit 2语法：语法精讲精练 动词不定式做主语 不定式作主语，表示具体的、一次性的或将来的动作；在很多情况下，人们通常用it作为形式上的主语，而把不定式移到谓语之后，使句子结构显得平稳一些。 To know something about English is one thing; to know English is quite another. 懂一点英语是一回事；掌握英语完全是另一回事。 It is impossible to learn a foreign language without making painstaking efforts. 想不下苦功就学会一门外语是不可能的。 一、动词不定式作主语的功能和意义 1. 不定式具有名词特征，可在句子中充当主语，其谓语动词用单数形式。 To know oneself is difficult. 人很难做到自知。 To love and to be loved is the greatest happiness one can get. 爱的同时也被爱是一个人能获得的最大幸福。 2. 动词不定式与动名词作主语的区别 (1)不定式：表示具体的某次动作，特别是将来的动作。 To teach you the uses of the infinitive is my job today. 教你们不定式的用法是我今天的工作。(表具体行为) (2)动词­ing形式：表示比较抽象的、经常性的、一般性的动作。 Teaching is my job. 教学是我的工作。(表抽象行为) 【即学即练1】单句语法填空 ①____________ (hear) your voice is so nice. ②____________ (look) after the safety of the community is his responsibility. ③____________ (smoke) is prohibited here. ④How to cure(cure) this kind of illness is still unknown. 二、it作形式主语的句型 1. It is＋形容词＋(for/of sb)＋to do sth It is necessary for us to master a foreign language. 我们有必要掌握一门外语。 It is very kind of you to help us. 你帮助我们真是太好了。 【名师点津】区别for 与of (1)for sb 常用于表示事物的特征、特点，表示客观形式的形容词，如easy, hard, difficult, interesting, impossible等。 It’s very hard for him to study two languages. 对他来说学两门语言是很难的。 (2)of sb一般表示人物的性格、品质，表示主观感情或态度的形容词，如good, kind, nice, clever, foolish, right等。 It’s very nice of you to help me. 你来帮助我，真是太好了。 2. It is ＋a/an ＋名词(pity/shame/pleasure/honour...)＋ to do... It’s a great honour to be invited to your birthday party. 很荣幸被邀请参加你的生日聚会。 3. It takes/costs/requires/makes...to do sth It took me two hours to finish the work. 我完成那项工作用了两个小时。 【名师点津】在“It is ＋ no use/no good/useless/fun/enjoyable/tiring/interesting/ foolish/nice/a waste of time/a pleasure...”句型中，常用动名词形式作真正的主语。 It is no use waiting here doing nothing. 无所事事地等待是没有用的。 【即学即练2】　完成句子 ①It seemed selfish of him ________________________. 他不给他们任何东西，这显得太自私了。 ②It seems a pity ____________. 拒绝似乎是遗憾的。 ③It’s unwise ________________________. 他们拒绝(采纳)这个建议是不明智的。 ④It will be a mistake