is that it?是什么用法? it is that 强调句用法
it is......that怎么用
1.It is + 被强调部分 + that ... 就是强调句
该句型是强调句型。将被强调的部分放在前面，其它部分置于that之后。被强调部分可以是主语，宾语，表语或状语。强调的主语如果是人，that可以由who换用。如果把这种句型结构划掉后，应该是一个完整无缺的句子。这也是判断强调句型与其它从句的方法。
It was about 600 years ago that the first clock with a face and an hour hand was made.
It was they that (who ) cleaned the classroom yesterday.
It was in the street that I met her father.
补充：
2. It is not until + 被强调部分 + that ...
该句型也是强调句型。主要用于强凋时间状语，译成汉语”直到．．．才．．．”，可以说是 not ... until ... 的强调形式。
It was not until she took off her dark glasses that I realized she was a famous film star.
= Not until she took off her dark glasses did I realize she was a famous film star.
= I didn’t realize she was a famous film star until she took off her dark glasses.
3. It is clear ( obvious, true, possible, certain....) that .....
该句型中it 是形式主语，真正的主语是that 引导的主语从句，常译为”清楚（显然，真的，肯定．．．）” 是主语从句最常见的一种结构。
It is very clear that he’s round and tall like a tree.
= That he’s round and tall like a tree is very clear.
4. It is important ( necessary, right, strange, natural...) that ...
该句型和上一个同属一个句型。由于主句中的形容词不同，that 后的从句中要用虚拟语气（should + 动词原形），should 可以省去。建议记住该句型中的形容词。
It is important that we (should) learn English well.
It is necessary that he (should) remember these words.
5. It is said (reported, learned....) that ...
该句型中的it 仍是形式主语，真正主语是that 引导的主语从句。该结构常译为”据说（据报道，据悉．．．）”。
It is said that he has come to Beijing.
It is reported that another earth satellite has been put into orbit.
6. It is suggested ( ordered ... ) that ...
该句型和上一个同属一个句型。主句中的过去分词是表示请求，建议，命令等词时，that 后的从句要用虚拟语气（should + 动词原形），should 可以省。常译为”据建议；有命令．．．）
It is suggested that the meeting ( should ) be put off.
It was ordered that we ( should ) arrive there in two hours.
7. It is a pity ( a shame ... ) that ...
该句型中，that后的从句一般用虚拟语气（should + 动词原形），should可省去．表示出乎意料，常译为”竟然”。没有这种意义时，则不用虚拟语气。
It is a pity that such a thing ( should ) happen in your class.
这种事竟然发生在你们班上，真是遗憾！
It is a pity that he is ill. 他生病了，真遗憾！
8. It is time ( about time ,high time ) that ...
该句型中that 后的从句应该用虚拟语气，值得注意的是① 常用过去时态表示虚拟．② 有时也用should + 动词原形，should 不能省。常译为”是（正是）．．．的时侯．．．”。
It is time that children should go to bed.
= It is time that children went to bed.
9. It is the first ( second ... ) time that ...
该句型要和上一个句型区别开来。该句型中的 that 从句不用虚拟语气，而用完成时态。
至于用什么完成时态，由主句的谓语动词的时态决定。如果是一般现在时，后面从句用现在完成时态；如果是一般过去时，后面从句则用过去完成时态。该结构中 that 可以省去；it有时用 this 替换．常译为”是第一（二）．．．次．．．”。
It is the first time I have been here.
= This is the first time I have been here.
it is that都有哪些句式
这是一个主语从句。而It's .....that是强调句
（1）主语从句。
It is important that students today master English.
It is reported that China will send up a series of spaceships in the 21st century.
It is a rule that everyone should obey the State’s laws.
It happened that they were out visiting their friends.
可以看出，此类主语从句的句子成分无论是主语、谓语、宾语，还是各种状语都是完整的，并且不能称到“It is…”结构中去。这就是判别主语从句的基本点。
（2）强调句。
先举一个重点成分句：昨天我在书店看见了他。I saw him at the bookstore yesterday.
现将此句变成分别突出主语、宾语、地点及时间状语的强调句：
A、It was I that/who saw him at the bookstore yesterday.
B、It was him that I saw at the bookstore yesterday.
C、It was at bookstore that I saw him yesterday.
D、It was yesterday that I saw him at the bookstore.
比较无重点叙述对象原句和由此转换来的强调句可以看出，强调句是把原句拆散，把要强调的部分如主语、宾语、状语移到“It is…”之后。如果把“It is…that”去掉，并把移走的部分放回到原位，句子还是完整的，这就是判别强调句的基本方法。再把主语从句和强调句加以对比；主语从句各成分不能移到“It is…”结构中，而强调句则可以把句子的主语、宾语、状语等成分移到“It is”结构后面，其余放在“that”后面。
如果“It is…”之后是地点状语、时间状语、介词短语或从句，“It is…that”必为强调句型。除上面所述的C、D例句外，再补充例证如下：
It was here/there that we took a picture of him last year.
It was last year he went abroad.
It was after I came here that I learned a lot.(我到此之后才学到很多东西。)
It was not until he came back that we had dinner.(直到他回来后我们才吃饭。)
另外，在强调句“It is…”中, it is后不会出现形容词、过去分词及谓语词形式，这些词用在带有主语从句的“It is…that-clause”结构中。
（3）“It is…that”结构中的that可能引出定语从句。
It is this dictionary that I am looking for everywhere.（这是我求之不得的词典啊。）
在这样的句型中，it不再是形式主语或无意义，而是说话人心目中的指代的“那个”。that是关系代词，介词for的后面乍看无宾语，实际是前移走了。又如：
It was the most fascinating place that we’ve visited.
It is ....that ..
1 主语从句 如 it is clear that he has failed
2 强调句型 如 it is clearly that he speaks.
3 it 是指示 代词 that 是同位语从句 或定语从句
如 it is the news that our team has won.
it is the news that he told me.本句也可以看作是强调句
4 it 表示时间天气距离等
如 it is so hot that we won't go out.
迷惑 强调句 的题
如 it was at seven clock ----he arrived 答案是that 这是强调句
it was seven clock ----he arrived 答案是when这是状语从句
it is three years -----he came here.答案是since这是状语从句
it is for three years ----he has been here 答案是that 这是强调句
it is that 强调句的错误用法
that is a pen