It 的用法
1. it 常用作形式主语代替真正的主语不定式、动名词或从句。
●It +be+ adj. + (for sb) +to do sth
※此处adj. 通常为描述事件的形容词：easy，difficult，hard，necessary，possible，likely，right，wrong，important，polite，clear，obvious，certain，useful，useless，dangerous…
●It +be+ adj + of sb+to do sth = sb be +adj to do sth
※此处adj. 通常为描述人的品质形容词：kind，nice，rude，cruel ，considerate，thoughtful，careful，careless，silly，foolish，stupid，clever，crazy, wise…
●It + be +no use/ good/ useless + doing It is a waste of time/money doing sth
eg: It is a waste of time talking to him.
●It + be + adj./ n. /v p. p. /ving+ that- clause
※It is (amazing/surprisng/shocking/astonishing/disppointing…)that…“令人吃惊/失望的是…”
※It is clear(obvious,true, certain…)that…
※It is/ was +adj (important/ necessary/ urgent/ essential/ natural/ vital )+that从句（should do）
※It is a pity/a shame/no wonder/strange+that从句表示“失望、惊奇、可惜、怀疑”等，should+v should不可省略
※It is suggested/ordered/desired/requested/required/insisted/proposed/demanded/commanded/advised/
recommended/urged+ that从句(shoud)+v
※It is +v-ed+ that从句…=sb./sth. is + v-ed + to do /to be doing/to have done
It is said (reported/learned/believed/thought/known/told/hoped/proved/universally acknowledged/ universally accepted/ universally recognized.....) that ...
eg: It is said that he will go abroad . = He is said to go abroad.
It is said that Bell invented the first telephone in the world.
= Bell is said to have invented the first telephone in the world.
It is universally acknowledged that dogs have an acute sense of smell.
It is important for us to master a second language.
It is considerate of you to turn down the radio when the baby is asleep.
It is no use crying over spilt milk.
It is a fact that English is being accepted as an international language.
It needs further discussion whether we’ll build a lab-oratory or not.
It is shocking that people in those areas should live in such overcrowded slums.
It is suggested that he not go there alone.
It is important that we should speak politely.
It is no wonder that he should have made progress.（失望）
It is a shame that he should break his promise.(责备)
It is a pity that he should miss a wonderful film.（失望）
It is strange that he should marry her.（惊奇）
2. it 作形式宾语，代替后面的真正宾语不定式、动名词或从句。
※find/ think/ feel/ make/ consider +it +adj. /n.(for sb) +to do sth/that从句.
※like/love/hate/appreciate + it + 从句
※take it for granted that从句“认为…理所当然”
※see to it that从句= make sure that从句“务必，确保。。。”
※depend on it that从句rely on it that从句“指望…放心…相信…”count on it that从句※put it that从句= say that从句
eg: I think it necessary to discuss with him about this.
I owe it to you that I have survived the disaster.
We shall leave it to him to settle the matter.
He saw to it that the work was finished on time.
The teacher made it clear that the students should follow the instructions in the lab.
I would appreciate it if you could help me with my English.
I like it in the autumn when the weather is clear and bright.
You may depend upon it that we'll never desert you.
She took it for grounded that her own son would study medicine.
I'm counting on it that you will come.
I put it to you that Robert offered you money for that information.
3. It +takes +sth +to do sth “做某事需要……”
It takes sb +时间+to do sth
eg: ①It takes much patience to do the work.
②It took us two hours to get there on foot.
4. It +be +(high/about) time +(that)……did /should do“（早）是该做某事的时候了”
eg: It is time that you went to school.
It is time that you should go to school.
5. It +is+the first (second…)time +that…have/has done “是某人第一（二，…）次做某事”
It +was+the first (second…)time +that…had done
（其中It 可换成This 或That，要特别注意此句型中主、从句的时态。）
6. It is / has been+段时间+since……（从句用一般过去时）“自从……已有多长时间了”
eg: It is almost five years since we saw each other last time.
7. It +is/ takes +long（段时间）+ before……
It + will take/will be+时间段+before+一般现在时“要过很久…才”
It + won’t take/won’t be+时间段+before+一般现在“不久…就”
It didn't take/wasn't+时间段+before+一般过去时“没过多久…就”
It took/was+时间段+before+一般过去时“过了很久…才”
eg: It will be a long time before we finish the dictionary.
It was not long before the thief was caught.
8. It用于强调句型中：
It is/ was +被强调部分+that +……
It is/ was +not until… +that +……
It was not until you told me that I had any idea of the plan.
It was not until midnight that he got back home
9. It +be +up to sb +to do sth “由某人负责做某事”
