2019-2020学年北师大版高中英语选修七同步课件：UNIT 21 HUMAN BIOLOGY PERIOD 5 .ppt

1、返回目录 Human BiologyUnit 21返回目录 Period FiveGrammar名词性从句返回目录 语法要点精析针对强化训练目录Contents返回目录 语法要点精析一、条件句和混合条件句在英语中，我们一般把条件句分为两种，即真实条件句和非真实条件句。非真实条件句亦可称为虚拟语气。虚拟语气表示说话人的愿望、假设、猜测或建议，而不表示客观存在的事实。返回目录 1if虚拟条件句if虚拟条件句主句与现在事实相反的假设if主语动词过去式(be动词用were)主语would/should/could/might动词原形与过去事实相反的假设if主语had过去分词主语would/should

2、/could/mighthave过去分词返回目录 返回目录 If I were a bird，I could fly.如果我是一只鸟的话，我就能飞了。If we had started earlier，we would not have missed the train.如果我们早点出发，就不会错过这班火车了。If he shouldnt come tomorrow，we would put off the meeting till next Monday.要是他明天来不了，我们将把会议推迟到下周一。返回目录【提示】：在if虚拟条件句中，如果从句谓语动词有 were/should/had时，可

3、 以 省 略 if，然 后 把were/should/had提到主语前面，形成部分倒装。Were I at school again，I would study harder.如果我可以再上一次学，我会更努力地学习。Had you come earlier，you would have caught the bus.如果你早一点儿到，你就会赶上那趟公交车了。Should it rain tomorrow，we would not go climbing.如果明天下雨，我们就不去爬山。返回目录 2混合条件句通常情况下，虚拟条件句和主句表示的动作发生的时间是一致的，但不一致时主从句动词的形式应根据

4、各自所表示的时间进行调整。我们把这种结构称为混合虚拟条件句、混合虚拟语气或错综虚拟条件句。可将其分为两种：(1)想象中的现在状态可能对过去有影响。If I were you，I would have taken his advice.如果我是你的话，我就接纳他的意见了。返回目录(2)想象的过去事件可能对现在有影响。If I had taken my raincoat with me this morning，I would not be wet now.如果今天早上带上雨衣的话，我现在就不会淋湿了。返回目录 3含蓄虚拟条件句有时虚拟的条件并不是直接通过条件句来表示，而是用一些词或短语或上下文暗

5、示来说明，我们称之为含蓄虚拟条件句或含蓄虚拟语气。(1)用介词(短语)表条件，如：but for，without。But for your advice，I couldnt have done it so successfully.要是没有你的建议，我就不会做得那么成功。返回目录(2)用连词(but，or)，副词(otherwise)表条件。I would have attended the party，but I was too busy.要不是我太忙，我就去参加那个聚会了。(3)分词短语暗示条件。Having known in time，we might have prevented th

6、e accident.要是及时得知的话，我们也许能阻止这场事故。Given more attention，the tree could have grown better.如果多留心的话，这棵树本来可以长得更好。返回目录(4)通过上下文表条件。I would have come to see you that day.Unfortunately，it was raining so hard.我本来打算在那天来看你的，不巧的是那天下大雨。返回目录 二、情态动词1概述情态动词表示说话人的语气和情态，如需要、可能、意愿和怀疑等。情态动词有一定的词义，但不完整，必须和主要动词的原形一起构成谓语，常用的

7、情态动词有：can，could，may，might，must，ought to，need，dare以及shall，should，will，would；下面短语也表达情态动词的意义：be able to，had better，have to，used to。返回目录 2情态动词的用法表示推测can(能)；may(可能)；could(可能)；might(可能)；must(一定)；should(应该)；ought to(应该)；will/would(会)表示义务、责任、必要性must(必须)；have to(不得不)；should(应该)；ought to(应该)；need(有必要)；neednt(

8、没有必要)；dont have to(不必)；had better(最好)表示能力can(能够)；could(能够)；be able to(能够)返回目录 表示请求、许可、禁止Can I？；May I？；Could I？(委婉形式)；Will you？；Would you please？；Shall I？；cant(不可以)；mustnt(禁止)表示习惯和倾向used to do(过去常常)；would do(过去的习惯行为)；will do(常常)表示意志will(与第一人称连用，意为“愿意”)；shall(与第二人称和第三人称连用表示命令、允诺或强烈的意愿)返回目录 3常见情态动词的用法(

9、1)can表能力。He can speak English.他会讲英语。表客观条件允许做某事。I can call you tomorrow.我明天可以给你打电话。返回目录 表推测(多用于疑问句和否定句)。That cant be Maryshes in hospital.那不可能是玛丽她在住院。(2)could表过去的能力。I could drive a car before I left school.毕业前我就会开车了。返回目录 表可能性(既可表示过去的可能性，也可表示现在的可能性，比can的程度要弱)。He said the news could be true.他说这消息可能是真的。

10、返回目录 用于委婉、客气地提出请求、想法、问题或陈述看法，回答时用原形。Could I use your dictionary?Yes，you can.我能用一下你的词典吗？行，可以。返回目录(3)may表征求对方的意见。May I sit here?我可以坐这儿吗？表允许You may come if you wish.如果你想来，你就来。返回目录 表可能性。We may meet her at the station.我们可能会在车站遇到她。表祝愿。May you succeed!祝你成功！返回目录(4)might表可以做的事或可能发生的事，might比may的口气委婉或表示实现的可能性更

11、小些。Thinking it might rain，I decided to go by car.我想可能会下雨，所以决定开车去。返回目录 may(just)as well，might as well，意为“不妨”，用于提出建议。You may as well have a try.你不妨试一下。表可能性。We might finish the task ahead of time.我们可能会提前完成这项任务。返回目录(5)must表必须做的事，着重主观看法。其否定式mustnt表示禁止。对其问句作否定回答时不用mustnt，而用neednt或dont have to。have to强调客观需

12、要。I must go now.现在我必须走了。返回目录 Must I go to work?No，you neednt./Yes，you must.我必须去上班吗？不，你不必去。/是的，你必须去。表推测，只用于肯定句，意为“一定”，常指有根据、有把握地推测。There must be nobody.那儿肯定没人。返回目录“偏要，硬要”(指做令人不愉快的事)。Must you shout so loudly?你非得喊这么大声吗？Why must it rain on Sunday?为什么偏偏在星期天下雨？返回目录(6)shall用于主语为第二、三人称的陈述句中，表示说话人给对方的命令、允诺、警

13、告、强制、威胁、决心等。You shall apologize to him.你要向他道歉。用于主语为第一、三人称的疑问句，表示征求对方的意见和指示。Shall I fetch some water for you?要我去给你拿些水吗？返回目录 用于主语为第三人称的陈述句中，表示条约、规定、法令等中的义务，常译为“应，必须”。Members of the club shall pay for registration.俱乐部成员应付注册资金。返回目录(7)should/ought to表推测，表示说话者进行尝试性的判断，常译为“按道理说应该”。With her talent and exper

14、ience，she should do well by herself.凭着她的才能和经验，她自己应该能做得很好。should可以表示说话者惊奇、怀疑、不满的情绪。He should be careless to such an important matter.他竟然对这么重要的事粗心。返回目录 should/ought to表“应该”，多表示责任、义务、道德、法律等方面。Every citizen should/ought to obey the law.每个公民都要遵守法律。返回目录(8)will表意愿、意志、决心。I will succeed.我会成功的。表示倾向或习惯性动作。Fish

15、 will die out of water.离开水，鱼会死的。返回目录 用于疑问句表示请求、邀请。Will you see a movie with me?你愿意和我去看电影吗？(9)would表过去的意志、愿望和决心。I felt he would go with me.我感觉他愿意和我去。返回目录 委婉地提出请求、建议，比will更委婉，肯定回答用will。Would you join us?你愿意加入我们吗？返回目录 表过去习惯性的动作。As a young man，he would play basketball.小的时候，他常常打篮球。(10)need常 用 于 疑 问 句 和 否

16、 定 句 中，否 定 式 为needntNeed I heat the dish?No，you neednt.我需要热一下菜吗？不，不必。返回目录(11)dare多用于疑问句、否定句和条件句中Whats the matterdarent you read what it says?怎么了你难道不敢把上面写的念出来吗？If you ever dare call me that name again，youll be sorry.你胆敢再那样叫我，你会后悔的。返回目录 4“情态动词have done”的用法could have done可能做了某事(用于否定句和疑问句)；过去本来可以做某事(实际上

17、并没有做)may/might have done可能做了某事neednt have done本不必做某事(实际上做了)cant have done不可能做了某事must have done一定做了某事返回目录 should/ought to have done本该做某事但实际上未做shouldnt/ought not to have done过去不该做某事但做了He couldnt have gone abroad.I saw him just now.他不可能出国了。我刚才还看见他了。I neednt have got up so early.我本来不必那么早起床的。返回目录 针对强化训练.

18、用所给词的正确形式填空1I didnt see your sister at the meeting.If she _(come)，she would have met my brother.2 If I hadnt had your help，I _(not，finish)the work ahead of time.3If he _(take)his doctors advice，he might still be alive.had comewouldnt have finishedhad taken返回目录 4If I _(be)you，I could pass the test.5I

19、f he _(come)here，he would tell us about it.6_(be)it to rain，the crops would be saved.7Had I turned off the electric heater，the house _(not，catch)fire.8 If we _(not，make)adequate preparations，the conference wouldnt have been so successful.werewere to come/came/should comeWerewouldnt have caughthadnt

20、made返回目录 9If you _(work)hard then，you would be in the university now.10But for the meeting，I _(go)home at the time.had workedwould have gone返回目录.用适当的情态动词填空1Tom comes from Australia and he _ speak English very well.2I heard you bought a new book._ I have a look?3 It is sunny today;we _ take an umbrel

21、la.4_ you like to have dinner with me?5_ we finish the composition in class?No，you _.canMayneedntWouldMustneednt/dont have to返回目录 6May I smoke here?No，you _.7He is so strong that I _ fight against him.8 We _ have received the letter yesterday，but it didnt arrive.9He _ swim when he was ten years old.

22、10_ you have a good time!mustnt/cantdare notought tocould/was able toMay返回目录.单句改错(每小题仅有1处错误)1If I am in your position，I would marry her.amwere2If he have taken my advice，he would have succeeded in the competition.havehad3If it rained last night，the ground would be wet now.it后加had返回目录 4Its surprising

23、 that Mary would love such a person as Jack.wouldshould5If he was free today，we would send him to Beijing.waswere6 The law says that drivers cant drive after drinking.cantmustnt7Dare you to tell your parents about your school records？删除tell返回目录 8A few years ago I might afford to bring my wife to this place for dinner.mightcould9If you may go，at least wait until the storm is over.maymust10She told him he ought not do it.not后加to