Unit 2 Section Ⅲ Learning about Language——动词不定式(短语)作主语（Word教参）-【状元桥·优质课堂】2021-2022学年新教材高中英语选择性必修第三册（人教版2019）

Section Ⅲ　Learning About Language——动词不定式(短语)作主语 用括号内词的适当形式填写下面教材中的句子并体会它们的语法特征 1．However, during this period, it can be easy for some of them __to_form__(form) bad habits. 2．__To_prevent__(prevent) harmful habits like these from dominating a teenager's life is essential. 3．__To_change__(change) bad habits is never easy, even with many attempts. 4．After all, it is not easy __to_break__(break) bad habits. 一、动词不定式作主语的概念 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；完全掌握英语是另一回事。 ►It is impossible to learn a foreign language without making painstaking efforts. 想不下苦功就能学会一门外语是不可能的。 二、动词不定式作主语的用法 1．不定式作主语通常位于句首 ►To love and to be loved is the greatest happiness one can get. 爱和被爱是一个人能得到的最大幸福。 ►To get up early is necessary. 早起是必要的。 ►To read without reflecting is like eating without digesting. 读书不思考，犹如吃饭不消化。 [即时训练1]——单句语法填空 (1)__To_teach__(teach) you the uses of the infinitive is my job today. (2)__To_look__(look) after the safety of the community is his responsibility. (3)__To_solve___(solve) this annoying problem is really out of the question. 2．it作形式主语代替不定式的几种形式 把it放在句首作形式主语，而把真正的主语——动词不定式(短语)放在后面。 ►It's not easy to work out the problem. 算出这道题不容易。 ►It is interesting to play with snow in winter. 冬季里玩雪是很有趣的。 it作形式主语时有三种情况： (1)常用形容词作它的表语。作真正主语的不定式通常有逻辑主语，一般用for短语来表示，即It is/was ＋adj.＋for sb to do sth(其中sb就是to do的逻辑主语)。 ►It's important for us to keep the water clean. 保持水质清洁对我们来说是很重要的。 [名师指津] 在“It is/was＋adj.＋for/of sb to do sth”结构中，若形容词侧重于评价人物的特性、特征，则构成不定式复合结构的介词应用of，此时形容词常为kind，nice，foolish等词，且sb与形容词之间可构成逻辑上的系表关系；若形容词侧重于描写不定式动作的特征、特点，则构成不定式复合结构的介词应用for。 ►It's very kind of you to say so. 你这样说真是太好了。(可以说：You are very kind.) (2)有时也接名词作表语。 ►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。 (3)It作形式主语时，还常用于“It takes/took/will take 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。