北师大版高中英语选修7课件:Unit 21 Period Five
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1、Unit 21 Human Biology,内容索引,单元写作A discursive essay,单元语法Conditional revision mixed conditionals & Modality,Period Five Grammar & Writing,单元语法 Conditional revision mixed conditionals & Modality,语法感知,语法导学,.用所给词的正确形式填空 1.If you had posted the letter,Joan (receive) it last Monday. 2.What would you say or
2、do if someone (call) you a fool? 3.If he (not,be) ill,he would have done something to help us. 4.If you had studied hard,you (be) a college student now. 5.I am not tired.If I were tired,I (have) a rest.,would have received,called,hadnt been,would be,would have,.用适当的情态动词填空 1.He know the answer for he
3、 is very confident. 2.Who the man over there be? It be Mr Wang.He has gone abroad. 3.He come here by train,but Im not sure. 4.He be at home now.He is usually at home at this time. 5.You run,for we have enough time to catch the train.,must,cant,may,should,neednt,can,语法精析,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
4、,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。,1.if虚拟条件句,动词过去式(be用were) should动词原形 were to动词原形,if主语,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 me
5、eting till next Monday. 要是他明天来不了,我们将把会议推迟到下周一。,注意:在if虚拟条件句中,如果从句谓语动词有were/should/had时,可以省略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 n
6、ot go climbing. 如果明天下雨,我们就不去爬山。,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。 (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
7、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。,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。 (2)用连词(but,or),副词(otherwise)表条件。 I would have attended the party,but I was
8、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 the 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。 (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
9、,不巧的是那天下大雨。,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。,2.情态动词的用法,3.常见情态动词的用法 (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 c
10、all you tomorrow.我明天可以给你打电话。 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。 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。,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 dict
11、ionary? Yes,you can. 我能用一下你的词典吗? 行,可以。,(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。 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!,(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小些。 Thinking it might rain,I decided to go by car. 我想可能
12、会下雨,所以决定开车去。 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。,(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强调客观需要。 I must go now.现在我必须走了。 Must I go to work? No,you n
13、eednt./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。 “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?,(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、警告、强制、威胁、决心等。 You shall apologize to him.你要向他道歉。 用于主语
14、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? 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。,(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 experience,she should do well by herself.凭着她的才能和经验,她自己应该能
15、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。 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。,(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 will die out of water.离开水,鱼会死的。 用于疑问句表示请求、邀请。 Will
16、 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。 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? 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常用于疑问句和否定句中,否定式为neednt。 Need I heat the dish? No,you neednt. 我需要热一下菜吗
17、? 不,不必。 (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。,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)
18、cant have done不可能做了某事 must have done一定做了某事 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。,高考链接,.用所给词的正确形式或适当的情态动词填空 1.In todays information age,the loss of da
19、ta cause serious problems for a company.(2018北京) 2.They might have found a better hotel if they (drive) a few more kilometers.(2018北京) 3.I cant find my purse.I (leave) it in the supermarket yesterday,but Im not sure.(2018天津) 4.If we (catch) the flight yesterday,we would be enjoying our holiday on th
20、e beach now.(2018天津),can,had driven,could have left,had caught,5.Samuel,the tallest boy in our class, easily reach the books on the top shelf.(2017北京) 6.If the new safety system (put) to use,the accident would never have happened.(2017北京) 7.My room is a mess,but I clean it before I go out tonight.I
21、can do it in the morning.(2017天津) 8.Do you have Bettys phone number? Yes.Otherwise,I (not,be) able to reach her yesterday.(2017天津),can,had been put,neednt,wouldnt have been,9. (be) it not for the support of the teachers,the student could not overcome her difficulty.(2017江苏) 10.Had the governments an
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