It 的用法和判别

一、It 的基本用法

I. it 作人称代词，通常代替无生命的东西或前面所谈的事情或情况：

1. Aluminium looks heavy but actually it is very light. 铝看起来重，但实际上（它）却很轻。
2. The switch completes the circuit when you close it. 当你合闸时，电闸把电路接通了。
3. This plan is without controversy the best. We must make a careful study of it. 这个计划无可争辩地是最好的，我们必须仔细研究（它）。
4. Most birds can fly, and their structure shows it. 大多数鸟能飞，它们的身体结构也表明了这一点。
5. It is the third time (that) John has been late, isn't it? 这是约翰第三次迟到，是吧？（反意疑问句）

注 1：英语代词比汉语代词用得多。英译汉时常可重复代词所代的名词（如第2句），有时甚至可以不译（如第 1, 3 句）。

注 2：It 有时可代表有生命的 baby, child 等，因为这些词并未明确表示性别，故只好用 it 和 its 作其代词. 例如：I saw your daughter and her baby yesterday. I didn't know whether it is a boy or a girl. 昨天我见到了你的女儿及她的婴孩。我（当时）不知道这婴孩是男孩还是女孩。

II. it 起着指示代词 this 和 that 的作用：

1. It is a very good translation. 这是一篇很好的译文。
2. We must overfulfil our production plan. It is our task. 我们必须超额完成生产计划。这就是我们的任务。（it 代表前句整个意思）

III. it 指季节、时间、距离（包括一些物理量）、自然现象和环境情况：

1. It is early spring. 这是早春季节。
2. It is very cold today. 今天很冷。
3. It is half past 5 o’cock. 五点半了。
4. It is ten miles to our plant. 到我们工厂有10英里距离。
5. It is five cubic metres in volume. 体积是5立方米。
6. It is sixty grams in mass. 质量是60克。
7. It is very quiet (或 noisy) in the classroom. 教室里很安静（或很闹）。
8. It rained (或 snowed) last night. 昨夜下雨（或下雪）了。
9. It is blowing hard. 现正在刮大风。
10. With automation, it is quite different. 有了自动化，情况就全然不同了。（it 表示情况。）

Ⅳ. it 作先行代词用。it 先在句中充当形式主语或形式宾语，而将真正的和逻辑上的主语或宾语（通常用不定式短语、动名词短语或从句表示之）移到后面去。例如：

A. it 作形式主语：

1. It is our duty to help him. 帮助他是我们的职责。
2. It was wrong of you not to help her. 你当时不帮助她是错误的。
3. It takes much time to carry out a test. 进行试验是要花费许多时间的。
4. It will be useless learning a theory without practice. 学习理论而没有实践是无用的。

注：关于动名词短语作真正主语的用法，主要看表语使用哪些词。可参阅第 54 节、Ⅳ-A 的第二个注。

1. How much does it cost to send a telegraph? 打一份电报花费多少钱?
2. It was necessary that the metal should melt at a low temperature. 当时那种金属有必要在低温下熔化。
3. It may surprise you to know that many metals were used as early as 1,000 B.C. 要是你知道早在公元前一千年就使用了许多金属，你也许会感到惊奇。
4. It is obvious that metals in common use are very important in our life. 显然，普遍使用的金属在我们生活中是很重要的。
5. It has been pointed out that their suggestion is reasonable to a certain degree. 已经指出，他们的建议在某种程度上是合理的。
6. How did it come about that you made a lot of mistakes in your homework? 你作业里出了很多错，怎么搞的？
7. It matters little who will do that. 谁去做那件事，关系倒不大。

B. it 作形式宾语：

(a) it 在某些动词后作直接宾语的先行代词；在具有宾语补语的句子里，在宾语补语后面再出现真正的直接宾语（一般以不定式短语、动名词短语表示之，但也有用 that 引出一个宾语从句）。上述某些动词系指：think, consider, feel, regard, find, tell, make, take, have（声称）等。

1. We consider it necessary to combine theory with practice. 我们认为理论联系实际是必要的。
2. We found it useless learning a theory without practice. 我们认为学习理论而没有实践是无用的。
3. We have made it clear that agriculture is the foundation of the national economy. 我们已说清楚了，农业是国民经济的基础。
4. I feel it an honour to be asked to speak here. 我应邀在此讲话，感到很荣幸。
5. We think it important that theory (should) be combined with practice. 我们认为，理论结合实际是重要的。（it 作宾语从句的先行代词.）
6. They have it that Mr.Wang is going to Beijing next week. 他们宣称王先生下周准备去北京。
7. They will leave it to you to decide. 他们要让你去决定。
8. I regard it as preferable that she should study here. 我认为她在这里学习更好。（it 作后面宾语从句的先行代词，as preferable 为宾语补语。）
9. May I take it that you will write me a letter? 我可以相信你会给我写信吧？（it 作 that 引出的宾语从句的先行代词。）先行代词

(b) it 先在介词后占介词宾语的位置，然后通过 that 引出一个介词宾语从句：

1. We will answer for it that this test is reliable. 我们愿意保证这项试验是可靠的。
2. You may depend upon it that they will support you. 你相信好了，他们会支持你的。
3. Don't worry. I’ll see to it that you’ll get your share. 别着急。我一定保证使你获得你名下的份额。

C. 科技文章中常见的 it 作从句的先行代词时的固定句型举例：

It is clear (或 obvious) that… 很清楚，…；
It must be admitted that… 必须承认…；
It appears (或 seems) that… 看来…，似乎…；
It is stated (或 said) that… 据说（或一般认为）…；
It is to be noted that…要注意…；
It is well known that… 众所周知…；
It happened that… 碰巧…；
It is certain that… 肯定的是…[不能用sure代替]；
It is doubtful that… 人们怀疑的是…；
It was surprising (或 amazing, astonishing) that…（当时）令人惊讶的是…；
It is estimated that… 据估计…；
It is found that… 人们发现…；
It will (或 can) be seen from this that… 由此可见…；
It follows that… 从而或这样一来（于是）…；
It became clear (或 obvious) that… 显然，…等

Ⅴ. It 用于加强语气。其句型是“It is (或 was)… that（强调人时也可用 who 或 whom)…。有时强调事物，也可用 which 代替 that. 但强调状语和状语从句时，只能用 that。

A. 强调主语：

1. It was the soldiers who saved many people from drowning in 1998. 在 1998 年正是这些战士拯救了许多人免于淹死。
2. It was Jenny and Linda who laid many suggestions before the commitee. 正是詹妮和琳达向委员会提出了许多建议。
3. It was they whom you praised for their spirit of the age. 当时你表扬的正是他们的时代精神。（意译。注意不要将 they 改为 them.）

B. 强凋宾语：

1. It is this molecular motion that we call heat. 就是这种分子运动我们称之为热。
2. It was the mobile phone which (或 that) I bought in Tianjin. 那时我在天津买的正是这个移动电话.

C. 强调状语或状语从句：

[原句] After 1978 their families began a new life. 1978 年以后，他们的家庭开始了新的生活。

1. [强调句] It was after 1978 that their families began a new life. 正是在 1978 年以后，他们的家庭开始了新的生活。（强调时间状语）
2. [强调句] It is in the information center that we work together with the programmers. 就是在这个信息中心内，我们同程序员一起工作。（强调地点状语）
3. It is not for their personal interests that they study hard. 他们不是为了个人利益才努力学习的。（强调目的状语的否定式，而原句是通过否定谓语来表示对状语的否定。）
4. It was to save a child from drowning that we parted with you。为救起溺水的小孩，我们才离开了你。（强调作目的状语用的不定式短语）
5. It was with some difficulty that he found the answer to his problem. 他费了不少劲，才找到了这个题的答案。（强调行为方式状语）
6. It is not to anybody that (或 whom) he lends his books. 他并不是把他的书对任何人都出借的。（强调状语）
7. It is only when the people have become masters of their own country that they can really live a happy life. 只有当人民当了国家的主人以后，他们才能真正地过幸福的生活。（强调时间状语从句）
8. It is because English is very useful that we study it hard. 正因为英语很有 用，我们才努力学习（英语）。（强调原因状语从句）
9. It was through (或 because of) his carelessness that his key was lost. 他的钥匙丢失正是由于他的粗心。（强调原因状语）
10. It was while reading her letter that I had the idea that I was going to visit her the next day. 正是在读她的来信时，我就萌发第二天就去访问她的念头。（强调有省略成份的时间状语从句）
11. It is the atmosphere that gives us life and protection and that warms and shields us by night from the terrible cold of outer space. 正是这个大气层给了我们生命和保护，也正是它使我们感到暖和并在夜里使我们免受来自外部空间的严寒侵袭。（被强调的词后接两个由 that 引出的从句。）

D. 固定的强调句型：“It was not until（或till）…that…，”之意为“直到……才……“。例如：

1. It was not until 1972 that we began studying English. 直到 1972 年我们才开始学英语。
2. It was not till evening that we took priority over them. 我们到晚上才比他们领先。
3. It was not until the teacher came that they began the test. 直到老师来了以后，他们才开始做这个实验。

E. 注意强调句型的疑问句词序和强调状语从句中的关联词时的词序

1. Who was it (that) came to see you yesterday? 是谁昨天来看你啦？（强调原句中主语。因 Who 是疑问词，按特殊疑问句规定，就置于句首。强调句型中的 it was 也按特殊疑问句规定，颠倒为 was it. 后面部分和原强调句后面部分一样，维持原状，只是句末加个问号。）
2. What was it that you found in the room last week? 上星期你在房间里找到的是什么啊？
3. When was it that he paid six yuan for a dictionary? 他花了六元钱买了一本辞典是什么时候啊？
4. How is it that they are late? 他们怎么会迟到的？

注：如果本句型用于名词从句，则其中 it is (或 was) 不颠倒：

1）I wonder who it was (that) first called computers electronic brains. 我不知道谁首先把计算机叫做电脑。（句中 who 是疑问词，但句子不是疑问句，故 it was 不颠倒词序。注意这种强调句型中还可省略 that。）
2）She couldn't say what it was that bothered her. 她说不出是什么打扰了她。（同上）
3）Whatever (news) it is that you have heard of, you must tell him in time. 不论你听到的是什么（消息），你必须及时告诉他。

Ⅵ. it 用于“It is a + 形容词 + 名词 + that…”特殊的习惯用法中，真正的句意与字面相反，可能是修辞性反语发展起来的一种句式。它具有含蓄的让步意味，大多译为：“无论怎样……的……也不会……”。例如：

1. It is a wise man that never makes mistakes. 无论怎样聪明的人，也难免要犯错误。（不能按字面译为强调句型：^※聪明的人才从来不犯错误。）
2. It is a long lane that has no turning. 无论怎样长的胡同，也会有拐弯的地方。（不能按字面译为强调句型：^※长的胡同才不拐弯。）
3. It is a wise father that knows his own child. 无论怎样聪明的父亲，也不会完全了解自己的孩子。（不能按字面译成强调句型：^※聪明的父亲才了解他自己的孩子。）

二、It 的用法和判別

Ⅰ. 如果 it 是人称代词，一般是代替前面的单数名词。只有在极少数情况下，代词 it 在前，所代的名词却在后面，例如：

Although we cannot see it, there is air all around us. 虽然我们看不见空气，但在我们周围都有空气。

II. It 作非人称代词，其后面内容都是表示自然现象、时间、度量衡等。

III. 如果是强调句型，则去掉“It is (或was)… that (或 who, whom, which)…” 三个词以后，剩下的词仍能单独组成一个完整句子。it 后的谓语是其它形式时，决不能构成强调句型。例如：

1. It is from the sun that we get light and heat. 正是从太阳那里我们得到了光和热。（强调句型）
2. It is known that matter is in constant motion. 大家知道，物质处于不断的运动中。（非强调句型，后面为主语从句。）
3. It has been found that all kinds of matter consist of atoms. 人们已经发现，各种物质由原子组成。（同上，后面为主语从句。）

上述第 1 句中去掉 "It is… that" 三个词以后，剩下部分仍能构成一个句子，故是强调句型。但第 2 句中按上法去掉 "It is…that…" 三个词，句中 known 就没法处理了。第 3 句谓语不是 is 或 was, 故决不是强调句型。

1. It is those who have never been to college but who are sending or hope to send, their children to college, who are much interested in what is going on at university campuses. 正是那些自己没有上过大学而目前正在送其子女上大学或希望送子女上大学的人才对大学校园内发生的事很感兴趣。（句中头两个 who 引出的是前后在意义上有转折的定语从句，第三个 who 才和句首的 It is those 构成强调句型。

Ⅳ. It 作形式主语或形式宾语，其后面必有一个真正主语或真正宾语。一般用不定式短语、动名词短语或用 that 引导的从句来作真正主语或真正宾语。