① It + be + adj (kind , wise , careless, clever …) + of sb to do sth
Eg: It is wise of him to make such a decision.他做出这样的决定是明智的。
② It + be + adj(easy , safe , common , normal …) + for sb to do sth
该句型中adj若为important, necessary, natural, possible, strange, vital, essential等可改为从句,从句用should+动词原形。.
Eg: It’s very dangerous for children to play with fire.
It is important for us to learn English well.
(= It is important that we (should) learn English well.)
③ It + be +V-ed( reported, believed, said, suggested…) + that 从句
该句型中：⑴若V-ed为reported, believed, said等常译为“据报道”，“据认为”，“据说”。⑵若V-ed为suggested, ordered, demanded, insisted等表示“建议”,“命令”的词，从句要用虚拟语气(should)+动词原形。
Eg: It is suggested that the book (should) be revised.
It’s said that Tom has been back from abroad.
(=Tom is said to have been back from abroad.)
④ It + be + n (a pity, a shame, a fact , good news…) + that 从句:
该句型中，从句一般用(should) + 动词原形，表示出乎意料，常译为"竟然"。
Eg: It is a pity that such a thing ( should ) happen in your class.
⑤ It is useless/no use/no good + doing sth
Eg : It useless arguing with him further.
It’s no use talking with him, because he won’t listen.
⑥ It takes sb. ... to do sth.
该句型中it是形式主语，真正的宾语是to do sth，常译为"做...要花费某人..."。
Eg: It took thousands of people many years to build the Great Wall.
1. sb find/ believe/ think/ feel/ consider/ make + it +n/adj +to do或从句
该句型中的it 作形式宾语。为了记忆方便我们可称该句型为“6123结构”。6 指主句中常用的动词：think, believe, make, find, consider, feel;1 指的是形式宾语 it;2 指的是宾补的两种形式：形容词或名词;3 指的是真正宾语的三种形式：不定式短语，动名词短语或that引导的宾语从句。
Eg: We think it our duty to clean our classroom every day.
He felt it important learning English well.
They found it difficult that they would finish their work in two days.
2. 主语+hate / dislike / love / like +it + when-从句
Eg: I hate it when people speak with their mouths full.
3. 主语+appreciate +it + if-从句
Eg: I really appreciate it if you could help me with my math.
4. sb. depend on/count on/rely on/ see to(负责，确保) / answer for it that…
Eg: You may rely on it that he won’t be late.
You must see to it that the doors are locked before you leave the lab.
5. sb. take it for granted that… 认为……是理所当然的
Eg: I take it for granted that he will succeed.
⑴ It + is+ 时间段 + since引导的时间状语从句:
Eg : It is 5 minutes since the bus left. 公汽开走已有5分钟了
⑵ It + be + 时间段 + before引导的时间状语从句:
Eg : It will be 3 hours before he comes back.要过三个小时他才会回来
It was 3 hours before he came back. 过了三个小时他才回来
⑶ It + be + 时间点 + when引导的时间状语从句
这个句型中, it 代指时间，表示时间点的词前没有介词。
Eg : It will be Monday when he comes back. 他周一的时候回来.
It was Monday when he came back. 他周一回来的.
对比：It was on Monday that he came back . (强调句)
⑷ It + is (about/high) time + (that) sb did/should do sth
意为“该是某人做…的时候了”， about/high是用于加强语气，that从句用should或动词一般过去时表虚拟。亦可转换成 It + is+ time +(for sb )to do sth.
Eg : It’s (high/about) time (that) we handed in/should hand in our homework.
⑸ It / This / That +is+ the first(second …) time + that sb has done sth:
意为“这是某人第…次做…”，注意time前有序数词，主句是 is 时 ，从句要用现在完成时;如果主句用was ，则从句须用过去完成时。
Eg : It is the third time that I have seen the film.
That was the second time that I have been there.
☆强调句形式：It + is/was +被强调的部分+ that/who 从句
Eg: It was last week that I met an old friend in the street.
It was because he was ill that he didn't come to school yesterday.
Eg: It is you，rather than he，that are to blame for the accident.
Eg: It was in the restaurant where we had dinner last Sunday that you left your wallet.
一般疑问句：Is / Was it + 被强调部分+ that + 句子其余部分 ?
Eg: Was it in 1933 that the Second World War broke out?
特殊疑问句：疑问词+ be + it + that + 句子其余部分?
Eg: When was it that he changed his mind to take part in the activity?
Eg: I don’t know when it was that he changed his mind to take part in the activity?
It is / was not until +被强调部分+ that +其他部分
Eg : It was not until midnight that she went back home.
此句型只用until，不用till。但如果不是强调句型，till和until可通用。因为句型中It is / was not...已经是否定句了，that后面的从句要用肯定句。
It looks / appears as if ... 看起来好像……
It seems that ... 似乎……
It turns out that... 原来是……
It occurs to/strikes sb that… 突然想到……
It happened that ... 碰巧……
It doesn’t matter whether/if…无论是…没关系
It is no wonder that 难怪…
It all depends/that all depends.那得看情况
It's up to sb.由……决定，由……负责，取决于……
as it is (1)事实上，实际情况是……; (2)照原样
Believe it or not.信不信由你
How did it come about that … “……怎么发生的?”
1. The boy became fatter and fatter each day and ___made his parents sad.
A.which B.what C.he D.it
2. Someone is ringing the doorbell. Go and see ______.
A.who is he B.who he is C.who is it D.who it is
3. In fact, ___is a hard job for the police to keep order in an important football match.
A.this B.that C.there D.it
4. Tom’s mother kept telling him that he should work harder, but ___didn’t help.
A.he B.which C.she D.it
5. Does___matter whether he can finish the job on time?
A.this B.that C.he D.it
6. ___used to be thought that the earth was square.
A.He B.What C.It D.That
7. I took ___for granted that he would believe in us.
A.that B.the thing C.it D.this
8. He lived in poverty, and he couldn’t help ___.
A.so B.such C.it D.that
9. We had to be patient because it___some time ___we got the full results.
A.has been ; since B.had been ; until
C.was; after D.would be ; before
10. ____four years since I joined the army.
A.There was B.There is C.It was D.It is
3.D。it作形式主语,真正主语为不定式复合结构for sb. to do sth.
8.C。can’t/couldn’t help (it)意为“是没有办法的事”，“控制不了”。