Unit2 Period Ⅱ Grammar-【优化探究】2023-2024学年新教材高中英语选择性必修第三册同步导学案配套教参（人教版）

Period Ⅱ　Grammar 单元语法：Infinitives as the subject (动词不定式作主语) 授课提示：对应学生用书第42页 [语法体会] 诵读下列例句并感知黑体部分的共性 (1)[教材原文] To change bad habits is never easy，even with many attempts. (2)[教材原文] To prevent harmful habits like these from dominating a teenager's life is essential. (3)[教材原文]However，during this period，it can be easy for some of them to form bad habits. 1．以上三句中黑体部分的动词不定式都作主语。 2．第三句中it作形式主语，真正的主语是动词不定式。 [知识精要] 1．表示单一概念的动词不定式作主语时，谓语动词用单数。 To love and to be loved is the greatest happiness one can seek.爱与被爱是一个人所能寻找的最大的幸福。 To see is to believe.眼见为实。 2．多数情况用it作形式主语，把真正的主语即动词不定式置于句末，特别是不定式短语较长时。 To learn English well is not easy. ＝It's not easy to learn English well. 学好英语不容易。 It is our duty to try our best to deal with these problems.尽力处理这些问题是我们的责任。 The head teacher said it was necessary to talk with his mother.班主任说有必要和他的母亲谈谈。 it作形式主语，不定式作真正的主语，常用于下列句式中： (1)It be＋名词＋to do It's our duty to take good care of the old.照顾好老人是我们的责任。 (2)It takes sb.some time to do How long did it take you to finish the work? 你花了多长时间完成这项工作？ (3)It be＋形容词＋for sb.to do It is hard for him to finish the work in three days.对他来说，在三天内完成这项工作很难。 (4)It be＋形容词＋of sb.to do “It is kind of you to help others，” the teacher says.老师说：“你帮助其他人，真是太善良了。” (5)It seems/appears＋形容词＋to do It seemed impossible to save money.省钱似乎是不可能的。 [名师点津]　(1)It be＋形容词＋for sb.句型中的形容词常用表示事物的特征、特点、客观形式的形容词，如easy，hard，difficult，interesting，impossible等。 (2)It be＋形容词＋of sb.句型中的形容词一般用表示人物的性格、品德、主观感情或态度的形容词，如good，kind，nice，clever，foolish，right等。 It's very hard for him to study two foreign languages.对他来说，学两门外语是很难的。 It's very nice of you to help me.你来帮助我，你真是太好了。 3．“疑问词＋不定式短语”作主语可置于句首。 How to learn English well is important.如何学好英语很重要。 4．动词不定式与动名词作主语的区别 不定式作主语 往往表示具体的或一次性的动作 动名词作主语 表示一般或抽象的行为动作 Playing with fire is dangerous.玩火是危险的。(泛指玩火) To play with fire will be dangerous.玩火将很危险。(指某一具体动作) [名师点津]　to do 和 doing 会在不同的特定句式中充当主语。 It is＋形容词＋to do (不定式作主语) It is useless/no use/no good doing sth.(doing作主语) It is no good arguing with him.He never liste