2020_2021学年高中英语Unit4Breakingboundaries突破语法大冲关教师用书外研版选择性必修第二册

Unit 4 Breaking boundaries INCLUDEPICTURE "突破+.TIF" \* MERGEFORMAT INCLUDEPICTURE "语法精讲.TIF" \* MER

Unit 4Breaking boundaries it 作形式主语 [观察例句] 1 ．It is difficult for aforeigner to learn Chinese. 2 ．It's kind of you to help me. 3 ．It is no use talking to him about it. 4 ．It is amystery to me how it all happened. 5 ．It is believed that the flood there is the biggest in 100 years. [归纳用法] it作形式主语时没有具体的意义，只是帮助把真正的主语移到句子后面去，使句子显得 平衡。it作形式主语时，真正的主语通常是不定式短语、­ing短语或主语从句。 一、不定式短语作真正的主语，常用于下列句型中： It ＋be ＋形容词 ＋(for/of sb.) to do sth. It ＋be ＋名词 ＋to do sth. It takes sb.some time to do sth.干……花了某人……时间 It's up to sb.to do sth.干……是某人的职责或义务 It is everyone's duty to obey the law. 遵守法律是每个人的义务。 It took them ayear to build the bridge. 建这座桥花了他们一年的时间。 It is bad manners to stare at people. 盯着人看是不礼貌的。 It is up to us to help those in need. 帮助那些有困难的人是我们的责任。 [名师点津] 在“It＋be＋形容词＋for/of sb.to do sth.”句型中，如果形容词描述的是sb.，则