It (so) happened(chanced) that +clause. = sb. happened /chanced to do sth. =sb.did sth.by chance. 如：
It happened that he was out when I got there. 当我到那儿时，碰巧他不在。=He happened to be out when I got there.= It chanced that he was out when I got there= He was out by chance when I got there.
句型2
It seems that sb. do/ be doing/ have done/ had done= Sb. seems to do/ be doing/ have done/to be done/to have been done(还有动词appear等可这样使用)如:
It seemed that he had been to Beijing before.他好象以前去过北京。=He seemed to have been to Beijing before.
句型3
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中的谓语动词否定的转移)。 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。)
句型4
It is high time (time/ about time)+ (that) 主语+should do / did+其它。(从句中的谓语动词用的是虚拟语气。)如:
It is high time that we should go / went home.我们该回家了。
句型5
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.
句型6
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。
句型7
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。
句型8
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。
句型9
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。)
句型10
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 cameback from the United States.
句型11
It is well-known that+从句。如：
It is well-known that she is a learned woman.众所周知，她是个知识渊博的妇女。
句型12
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)
注意下列句型的翻译:It is five years since he lived here.他从这儿搬走已经有五年了。
句型13
It +谓语+段时间+before+主语+谓语.( before引导的是时间状语从句。) 如：
It wasn't long before the people in that country rose up.没有多久那个国家的人民就起义了。
It will be three hours before he comes back.三个小时之后他才能回来。
句型14
It is +形容词(possible, impossible, necessary等) +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。
句型15
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。
句型16
由as引导的非限定性的定语从句。如：
As we have known, he is a most good student.众所周知，他是个很好的学生。请比较：It is well-known that he is a most good student.(前一个是定语从句，而后者是个主语从句。)
With fresh water, the world will be prosperous.
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