第二步：语法精讲
　　1. 简介
　　(1) 一般情况用It is (was)…that (who)…，指人时，用who；指物时，用that。
　　我们分别可以强调主语、宾语、表语、时间状语和地点状语等。如：
　　He read three books in the library yesterday.（正常句子）
　　It was he who read three books in the library yesterday.（强调主语）
　　It was three books that he read in the library yesterday.（强调宾语）
　　It was in the library that he read three books yesterday.（强调地点状语）
　　(2) 强调状语或定语时，只用that，不用when、where，如：
　　It is at 5 o’clock that the train will arrive.
　　(3) 被强调的部分是主语时，注意句子的谓语动词和被强调的主语保持一致。如：
　　It is he who is late.
　　It is they who were late.
　　(4) 一般疑问句的强调句为“Is (was) it + that…?”；特殊疑问句为：“特殊疑问词+ is (was) +it +that…?”结构。如：
　　Was it ten years ago that his father died?（他的父亲是十年前去世的吗？）
　　When is it that you will set off?（你到底什么时候出发？）
　　(5)“not…until…”句型的强调结构为“It is not until…that…”应注意把否定词not转移到until前面。如：
　　I didn’t go home until the rain stopped.（直到雨停了我才回家）。
　　强调句为：It was not until the rain stopped that I went home.
　　I didn’t know the news until yesterday.（直到昨天我才知道那个消息）
　　强调句为：It was not until yesterday that I knew the news.

　　2. 四级必考套句学习
　　(1) It is the responsibility of to do sth.
　　【分析】注意，从形式上看该句子很像强调句型，而实际上并非如此，因为句中it是形式主语，动词不定式作实际主语。
　　It is the responsibility of every citizen in our society to do his utmost to protect the environment.
　　(2) It is the , I suppose, that have\has given rise to .
　　【分析】该强调句型强调句子主语，I suppose作为插入语。这是一个很好掌握的四级长句，在作文中需要分析原因时，可以用它阐述自己的看法。
　　It is the tighter job market, I suppose, that has given rise to the increase in the number of unemployed college students in China.
　　(3) It is only when that .
　　【分析】强调句型强调when引导时间从句。
　　It is only when you nearly lose someone that you become fully conscious of how much you value him.

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