1.It is / was＋被强调的部分＋that(who)+剩余的部分.如：
It wasn’t until he came back that I went to bed.直到他回来我才睡觉。(一定要注意被强调句型谓语动词否定的转移，及形式)。
It was because he was ill that he didn’t come to school today.只因为他有病了今天没有来上学。（只能用because而不能用for, as 或since）
It is I who am a student. 我确实是个学生。（句中am不能用are来代替。）
2.It is high time (time/ about time) (that) 主语＋should do / did+其它。（注意从句中的谓语动词用的是虚拟语气）
It is high time that we should go / went home.我们该回家了。
3.It is / was said ( reported…)＋that+从句. 如：
It was said that he had read this novel.据说他读过这篇小说。＝He was said to have read this novel.
4.It is impossible / necessary/ strange…that clause.(从句中的谓语用should＋do / should have done，其形式是虚拟语气。)如：
It is strange that he should have failed in this exam.真奇怪，他这次考试没有及格。
5.It is + a pity/ a shame…that clause.(注意从句中的谓语动词用should do或should have done的形式，但should可以省略。)如：
He didn’t come back until the film ended. It was a pity that he should have missed this film. 他直到电影结束才回来。他没有看到这部电影真可惜。
6.It is suggested / ordered/ commanded /…that +clause.(从句的谓语动词用should do, 但should可以省略。)如：
It is suggested that the meeting should be put off.有人建议推迟会议。
7.It is/was＋表示地点的名词＋where+从句。（注意本句不是强调句型，而是以where引导的定语从句。）如：
It was this house where I was born.请比较：It was in this house that I was born. (后一句是强调句型。)
8.It is / was +表示时间的名词＋when+从句。（注意本句型也不是强调句型，而是以when引导的定语从句。）如：
It was 1999 when he came back from the United States. 请比较：It was in 1999 that he came back from the United States.
9.It is well-known that＋从句。如：
It is well-known that she is a learned woman.
10.It is +段时间＋since+主语＋did. 请比较：
It was +段时间＋since+主语＋had done. 如：
It is five years since he left here.他已经离开这儿五年了。
It was five years since he left here.（同上）
11.It is +形容词＋for+ sb.+ to do. 如：
It is impossible for me to finish this work before tomorrow.我明天之前完成此工作是不可能的。
It is +（心理品质方面的）形容词＋of + sb. + to do. = 主语+ be +形容词＋to do.(常用的形容词有：kind, stupid; foolish, good, wise等。)如：
It is kind of you to help me.＝You are kind to help me.你真好给我提供了帮助。
12.It is／was not until…that
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