高中英语基本句型*It (so) happened（chanced） that +clause. = sb. happened /chanced to do sth. = sb.did sth. by chance.：当我到那儿时，碰巧他不在*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:他好象以前去过北京。
*It is / was＋被强调的部分＋that(who)+剩余的部分.如：只有学会了给予我们才能体会索取的价值。
(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.（只能用because 而不能用for, as 或since）It is I who ___(be)a student. 我确实是个学生。
*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。
）It is high time that we____(go) home.我们该回家了。
*It is / was said ( reported…)＋that+从句. 如：It was said that he had read this novel.＝He was said to have read this novel. 每个人都知道阅读对我们有好处*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。
)It is strange that he should have failed in this exam.真奇怪，他这次考试没有及格。
*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)He didn't come back until the film ended. It was a pity that he should have missed this film.*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。
*It is well-known that＋从句。
如：众所周知，长城是著名的历史遗迹，吸引了众多国内外的游客。
*It is +段时间＋_____+主语＋did. 请比较：*It was +段时间＋______+主语＋had done. 如：It is five years _____ he left here. It was five years _____ he had left here.*It +谓语＋段时间＋_____+主语＋谓语.It wasn't long ______ 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______he comes back.三个小时之后他才能回来。
*It is +形容词(possible, impossible, necessary等) ＋____+ sb.+ to do. It is impossible ____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。
)It is kind of_____you to help me.＝You are kind to help me.*由as引导的非限定性的定语从句。
如：_____ we have known, he is a most good student. 比较：It is well-known ____he is a most good student.*由which引导的非限定性的定语从句。
如：He is a professor, which I have been looking forward to becoming.由where, when引导的定语从句（其中包括限定性的或非限定性的。
）如：This is the house _____I used to come.请比较：This is the house which / that I used to come to.This is the day ______ I joined the Party.请比较：This is the day which / that I joined the Party on.三、让步状语从句No matter what / which / who / where / when / whose＋从句，＋主句.(注意从句中的时态一般情况下用一般现在时态。
)No matter what you do, you must do it well.比较：Whatever you do, you must do it well.No matter where you go, please let me know.请比较：Wherever you go, please let me know.老师鼓励我无论遇到了什么困难，都不应该失去信心。
无论我们身在何处，都应该和父母保持联系。
四、条件状语从句When / So long as / As long as / Once/ If +从句，＋主句。
（从句也可以放在主句之后。
）如：如果我们处在很大的压力下，我们就无法集中精力学习；如果压力太大，我们就会失眠。
一旦你开始学习英语，你应该把它学好。
主句＋on condition that+从句.如：I will go with you on condition that you give me a sum of money.主句＋_____+从句.(注意：由于_____本身是否定词，所引导的从句的谓语动词用肯定而不用否定。
)如：I will go there tomorrow______ it rains.我明天去那儿除非下雨。
祈使句，＋_____/_____+主句。
（注意：祈使句也可用一个名词短语。
）如：Use your head, _____you will find a good idea. Another word, _____I will beat you.Hurry up ____ we will be late.If +necessary / impossible/ important等，＋主句.(注意：if与形容词之间的it is被省略。
)If necessary, I will do it. 如果可能，我们应尽量使用环保袋而不是塑料袋。
主句＋in case+从句.（in case表示以免）如：I will take my raincoat in case it rains.主句＋due to / because of / owning to / + the fact _____ +从句。
如：He did not come to school because of the fact_____t he was ill.When / While / As +从句，＋主句.如：当我和父母有分歧时，我会耐心的和他们交谈，告诉他们我的想法，尽力争取他们的支持。
主句＋after / before +从句. 如：They hadn't been married four months _____they were devoiced. We went home_____we had finished the work.主语＋肯定谓语＋until＋从句.请比较：主语＋否定谓语＋until+从句.如：I worked until he came back.我一直工作到他回来。
I didn't worked until he came back.他回来我才开始工作。
As soon as / Immediately / Directly / Instantly / The moment / The instant / The minute +从句，＋主句. 如：My father went out _____（immediate）, I got home.No sooner +had + 主语＋done…____ +主语＋did. 比较：主语＋had + no sooner +done…_____+主语＋did. 如：No sooner had I got to Beijing ____I called you.比较：I had no sooner got to Beijing _____ I called you.Hardly/Scarcely/ Rarely +_____+主语＋done…when / before + 主语＋did. 比较：主语＋____+hardly/Scarcely/ Rarely + done…when / before +主语＋did. Hardly_____ she had supper when she went out.请比较： She had hardly had supper when she went out.By the time+从句，＋主句.（注意时态的变化。
）如：By the time you came back, I ____ (finish) this book. By the time you come back, I______ (finish) this book.each / every time +从句，＋主句. (这时相当于whenever 或no matter when引导的从句。