高中英語語法：It 所構成的20個句型詳解
1. It is + 被強調部分 + that …
該句型是強調句型。將被強調的部分放在前面，其它部分置于that之后。被強調部分可以是主語，賓語，表語 或狀語。強調的主語如果是人，that可以由who換用。如果把這種句型結構劃掉后，應該是一個完整無缺的句子。這也是判斷強調句型與其它從句的方法。
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.
2. It is not until + 被強調部分 + that …
該句型也是強調句型。主要用于強凋時間狀語，譯成漢語“直到…才…”，可以說是 not … until … 的強調形式。
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 ……
該句型中it 是形式主語，真正的主語是that 引導的主語從句，常譯為“清楚(顯然，真的，肯定…)” 是主語從句最常見的一種結構。
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 …
該句型和上一個同屬一個句型。由于主句中的形容詞不同，that 后的從句中要用虛擬語氣(should + 動詞原形)，should 可以省去。建議記住該句型中的形容詞。
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 …
該句型中的it 仍是形式主語，真正主語是that 引導的主語從句。該結構常譯為“據說(據報道，據悉…)”。
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 …
該句型和上一個同屬一個句型。主句中的過去分詞是表示請求，建議，命令等詞時，that 后的從句要用虛擬語氣(should + 動詞原形)，should 可以省。常譯為“據建議;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 …
該句型中，that后的從句一般用虛擬語氣(should + 動詞原形)，should可省去。表示出乎意料，常譯為”竟然“。沒有這種意義時，則不用虛擬語氣。
It is a pity that such a thing ( should ) happen in your class.這種事竟然發(fā)生在你們班上，真是遺憾!
It is a pity that he is ill. 他生病了，真遺憾!
