湖南 林文发 胡辉
　　
　　It作引导词，用于强调结构，一般用来强调陈述句中除谓语动词以外的大多数句子成分，包括主语、宾语、状语和相关从句等，用来加强语气。这种强调句型一般用“It be +被强调部分+that（who）+其它部分”来构成，常用于现在时和过去时。如：
　　
　　I happened to meet Tom in the street the day before yesterday.
　　
　　我前天碰巧在街上遇见了汤姆。
　　
　　It was Tom that I happened to meet in the street the day before yesterday.
　　
　　前天我在街上碰巧遇见的是汤姆。
　　
　　It was I who / that happened to meet Tom in the street the day before yesterday.
　　
　　是我前天碰巧在街上遇见了汤姆。
　　
　　It was in the street that I happened to meet Tom the day before yesterday.
　　
　　我前天是在街上碰巧遇见的汤姆。
　　
　　It was the day before yesterday that I happened to meet Tom in the street.
　　
　　我是前天碰巧在街上遇见了汤姆。
　　
　　I. 如果强调的部分是人，则人称代词须保持原来的形式，这时连接词可用who, whom代替that。如：
　　
　　It is he who / that teaches us French.
　　
　　是他教我们法语。
　　
　　It is us who / whom / that he teaches French.
　　
　　他是教我们的法语。
　　
　　II. 如果强调句子中的地点、时间或原因状语时，连接词仍用that，不能用where, when或why。如：
　　
　　It is at the street crossing that I met one of my classmates that I had not seen for ages.
　　
　　我是在十字路口碰到了我多年未见的老同学。
　　
　　It was last month that I took part in the Palace ball.
　　
　　我是在上个月参加的宫廷舞会（不能用when）。
　　
　　It was for this reason, I suppose, that the book took a long time to come out.
　　
　　我想正是由于这种原因使得那本书很长时间才出版（不能用why）。
　　
　　III. 当强调not…until结构时，须将not until连用，后面接肯定式。如：
　　
　　It was not until at that time that I realized what trouble he was in.
　　
　　直到那个时候我才意识到他有什么麻烦。
　　
　　It was not until the bell rang that the teacher stopped his lesson.
　　
　　直到铃响了老师才下课。
　　
　　IV. 强调句型的一般疑问句须将be的形式提前，放在句首。如：
　　
　　Was it she who said it like that?
　　
　　是她那样说的吗？
　　
　　Was it the book of this kind that they liked in their childhoods?
　　
　　他们在孩提时代喜欢的是这种书吗？
　　
　　Can it be Jack that stole the purse of the woman?
　　
　　是杰克偷了那妇女的钱包吗？
　　
　　V. 强调句型还可用特殊疑问句。如：
　　
　　What was it that started the big fire in the building?
　　
　　到底是什么原因引起那栋大楼的大火？
　　
　　When was it that she returned the book to the library?
　　
　　她是什么时候把书还回图书馆的？
　　
　　Where was it that he had worked before he came to this place?
　　
　　他在来这之前到底在哪儿工作呢？
　　
　　VI. 强调句型与主语从句的区别：强调句型可以还原成正常语序的句子，也就是说，强调句型中去掉It be… that后，句子仍然通顺，意义也依然完整，只是没有那么强调突出。而含主语从句的复合句中的it是指示代词，后面多为系表结构或被动语态。如果去掉It be…that，句子就不通顺了。如：
　　
　　It was in the lab that was taken charge by Professor Harris that they did the experiment.
　　
　　他们正是在哈里斯教授负责的实验室里做的实验。（=They did the experiment in the lab that was taken charge by Professor Harris.）
　　
　　It is certain that he is honest and modest.
　　
　　很显然，他是诚实而谦虚的。
　　
　　It is known to all that paper was made first in China.
　　
　　众所周知，纸是中国人最早制造出来的。
　　
　　摘自 考试报