7.it的用法
①用作人称代词,代替前文提到的事情。
This bike is not mine. It’s Peter’s.
②用以代替提示代词this, that
—What is this? —It’s a pen.
—Whose book is that? —It’s Mike’s.
③起指示代词的作用,指一个人或事物
—Who is knocking at the door? —It’s me.
—Who is making such a noise. —It must be the children.
④指环境情况等。
It was very quiet at the moment.
⑤指时间，季节，天气，气候等
—What time is it? —It is eight o’clock.
It often rains in summer.
⑥指距离
It is five kilometers from the office to my home.
It is a long way to the factory.
⑦作形式主语和形式宾语
当动词不定式,动名词或从句作主语时,通常把它们放在谓语之后,而用it作句子的形式主语
It is not easy to finish the work in two days.
It is not a good habit to stay up late.
It is no use crying over split milk.
It is a pity that you didn’t read the book..
当复合宾语中的宾语是不定式,动名词,宾语从句时,往往把宾语放在它的补足语后面,而用it作形式宾语,放在宾语补足语之前
I think it no use arguing with him.
I found it very interesting to study English.
He made it clear that he was not interested in this subject.
注意：see to it that…(务必)和take it for granted that…(想当然)句型中的it，以及词组make it
中的it(做事成功，搞定)。
⑧用于强调结构(详见专题九)
要强调句子的某一部分(通常是主语,状语,宾语), 可以把it 当作先行词.这种句子的结构是 “It is(was)+被强调部分+that (who )+句子的其余部分” .如果强调的部分是人,可用who whom 代替that
I met an old friend in the park yesterday.
此句各部分被强调后句型如下：
It was I who /that met an old friend in the park yesterday.
It was an old friend who/ that/whom I met in the park yesterday.
It was in the park that I met an old friend yesterday.
It was yesterday that I met an old friend in the park.
