Unit 4 Breaking Boundaries Grammar it作形式主语课件-2022-2023学年高中英语外研版（2019）选择性必修第二册

XB2U4 Grammar ——Hilda 1 你学过哪些it作形式主语的句式？ it 作形式主语的用法？ 主语部分相对于谓语部分而言太长，常把主语部分移到句尾，在主语位置放上it。 it 没有具体的意义，仅用于维持句子结构平衡，避免主语太长，显得头重脚轻。 it作形式主语主要有三种情况：代表不定式作形式主语、代表动名词作形式主语、代表从句作形式主语。 it 代表不定式作形式主语 It is impossible to get there by boat. It is difficult for a foreigner to learn Chinese. It is kind of you to help me. It + be + adj. + to do sth. It is adj. for sb. to do sth. & It is adj. of sb. to do sth. 两者区别？ adj.描述人的品质、品格，介词用of；adj.描述不定式所表示动作的特征，介词用for。 it 代表不定式作形式主语 It was her duty to clean the room. It is not a good habit to stay home too late. It + be + n. + to do sth. it 代表不定式作形式主语 It was against my principle to do that. It + be + p.p. + to do sth. p.p.=prepositional phrase it 代表不定式作形式主语 It cost 150 yuan to buy the dress. It took the workers almost three years to finish building them. It + vt. + O. + to do sth. vt.=transitive verb O.=Object it 代表不定式作形式主语（小结） It + be + adj. + to do sth. (for & of 区别) It + be + n. + to do sth. It + be + p.p. + to do sth. It + vt. + O. + to do sth. it 代表动名词作形式主语 常用于以下结构中： It + be + adj. + doing sth. It is pleasant sitting here. It + be + n. + doing sth. 其中常见结构有： It is no use/no good/ no fun/ useless/ a waste of time doing sth. 做某事没有用/没有好处/没有意思/没有用/浪费时间。 It is no use crying over spilt milk. = It is useless crying over spilt milk. 覆水难收。 it 代表从句作形式主语 it代表的从句可以用that来引导，也可以用whether /if、连接代词或连接副词引导。 It is obvious that students should get well prepared for their future. It is doubtful whether she will be able to come. It is a mystery to me how it all happened. it 代表从句作形式主语 It is natural that she knows everything about it. It is necessary that the work should be done. It + be + adj. + that ... it 代表从句作形式主语 It is a pity that you didn’t see such a good film. It is our hope that in coming decades, advances in science will offer new perspectives from which to study how people manage their lives. It + be + n. + that ... 常见于： It is a pity/a shame/a fact/an honour/ good news/no wonder/a wonder/...+ that... it 代表从句作形式主语 It is said