2. 在强调原因状语从句时，只能强调由because所引导的从句

It was because he was ill that he didn't come to school yesterday.

It is/was+被强调部分+ that(who)… 强调句型用来强调谓语动词以外的任何句子成分。当被强调部分是人时也可以用who。

在使用强调句型时需注意以下几点：

1. 请注意强调句型的特殊疑问句　

When was it that he changed his mind to take part in the activity？

3. S+ v. +it + prep. + that…

owe it to sb. that…把…归功于…

leave it to sb that…把…留给某人去做

take it for granted that …想当然

keep it in mind that…

Don't bother to arrange anything. Just leave it to me to sort out.

Don't　 take it for granted that all those who get good grades in the entrance examination will prove to be most successful.

注意：it用在不能直接跟宾语从句的动词后面，尤其是表示好恶的动词后，enjoy, like, love, dislike, resent, hate, don't mind, be fond of, feel like, see to　 宾语从句紧跟it之后

I hate it you can swim so well and I can't.

I’d appreciate it if you would like to teach me how to use the computer.

2..S+ v+it+ important/unimportant/necessary/unnecessary/natural/essential that sb (should) do sth

S+v+it+of much/great/no/little importance that…(should)…

(动词常为think, believe, suppose, consider, feel, make, keep…)

I think it important that you (should) attend the conference.

当句子的真正宾语是动词不定式、动名词或从句时，为避免句子头重脚轻，须将其放在宾语补足语之后，改用先行词it占据其原来的位置

it用作形式宾语的句型为：

1..S+V+it+adj/n+(for/of sb) to do／v-ing／that clause。

该句型中宾语补足语可由形容词、名词等充当。 (动词常为think, believe, suppose, consider, feel, make, keep…)

I think it hard for you to do the task on your own./I think it hard that you'll do the task on your own.

He found it not easy to learn a foreign language well．他发现学好一门外语是不容易的

We think it no good reading in bed．我们认为躺在床上看书无益处

4.It / this /that is the best/worst/most… that sb have done“这是那是某人经历过的…中最…的了。”

It /this/that was the best/worst/most… that sb had done

It was the best novel he had read before.

3．It +cost／costs +sb．+some money +to do sth． “某人花多少钱做某事”。

It cost me 260 yuan to buy the new watch．我买这块新手表花了260元。

2．It takes(sb．)some time to do sth=sb takes some time to do sth “(某人)花……时间做某事”。

It took me a week to finish reading the book．我花了一周时间看完这本书。

It took the men a week to mend our roof.(= The men took a week to mend our roof.)

1．It +is ／was +one's turn(duty，pleasure) +to do sth．“该轮到某人做某事(做某事是某人的责任、愉悦的事)”　

It's your turn to be on duty tomorrow．明天轮到你值日了。

6.It +v. (to sb) that clause= sb +v. to do sth

(用于这种句型的动词常为appear, seem, come about, emerge, follow, chance, happen, occur, transpire, turn out , work out)

It (so) happened/chanced that they were out.(= They happened/chanced to be out.) 碰巧他们出去了。

It seems that he is ill．＝He seems to be ill．看起来他好像病了

It作主语的常见句型：