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1、Unit21 Human Biology-语法篇_1、掌握混合条件句中的虚拟语气的用法。2、情态动词的用法。混合条件句中的虚拟语气混合条件句主句是指条件句中含有不同的条件结构，谓语动词所表示的动作和条件从句谓语动词所表示的动作并不是同时发生,如一个与过去事实相反，另一个与现在事实相反。在这种条件句中， 动词的形式要根据具体情况进行调整。非真空条件从句主句If it had rained last night,it would be very cold today.If I had taken your advice,I would have no trouble with the work n
2、ow.If I were you,I would have gone to see the film last night.If he had told me about it, I would known what to do nowIf you had followed the doctors advice (then), you would be all right now.如果你那时听了医生的话,你现在就好了.(主句与从句发生的时间不同,应按照主句与从句各自的时间做调整.)If you had watered them more, the crops would be growing
3、still better.如果你再给庄稼多浇些水,他们会长得更好.(指现在长得更好.)If you had watered them more, the crops would have grown still better.如果你早就给庄稼多浇些水,他们就会长得更好(表示对过去的虚拟)情态动词一定义情态动词是一种本身有一定的词义,但要与动词原形一起使用，给谓语动词增添情态色彩，表示说话人对有关行为或事物的态度和看法，认为其可能、应该或必要等。情态动词后面加动词原形。二分类： 情态动词有四类： 做情态动词：must,can(could),may(might),ought to 可做情态动词又可
4、做实义动词：need,dare 可做情态动词又可做助动词：shall(should),will(would) 具有情态动词特征：have(had) to,used to三常用情态动词的用法1.must和have to表示必要性2.cant表示不可能， mustnt表示不允许或禁止3.dont have to和neednt表示没有必要4.can 和could 表示能力和可能性， 还可表示请求允许5.must,might,could表示猜想和推测6.may表示可能和允许四情态动词+have+过去分词1. “must+have+done”表示对过去事情的肯定推测，译成“一定做过某事”，该结构只用于肯
5、定句。 1). It must have rained last night, for the ground is wet. 昨晚一定下雨了，因为地面还是湿的。 2). You must have been mad to speak to the servant. 你和仆人说话，一定是发疯了。 2. “cant+have+done”表示对过去事情的否定推测，译成“不可能做过某事”。 1). Mr. Smith cant have gone to Beijing, for I saw him in the library just now. 史密斯先生不可能去北京了，我刚才还在图书馆见过他。 2
6、). Mary cant have stolen your money. She has gone home. 玛丽不可能偷你的钱，她回家去了。 3. “can+have+done”表示对过去行为的怀疑，用于疑问句，译成“可能做过吗？”。 1). There is no light in the room. Can they have gone out? 屋里没有灯，他们可能出去了吗？ 2). There is nowhere to find them. Where can they have gone? 到处找不到他们，他们可能到什么地方去呢？ 4. “could+have+done”是虚拟
7、语气，表示对过去事情的假设，意思是本来能够做某事而没有做。 He could have passed the exam, but he was too careless. 本来他能够通过考试，但是他太粗心。 5. “may+have+done”表示对发生过去的事情的推测，意思是“可能已经”或“也许已经”，用于肯定句中。 What has happened to George? I dont know. He may have got lost. 乔治发生了什么事？我不知道，他可能迷路了。 “might+have+done”表示对过去事情的推测，might与may意思相同，但可能性更小。多用于虚
8、拟语气结构中。 1). He might have given you more help, even though he was busy. (MET90) 他或许会多给你一些帮助，即使他很忙。 2). She might have achieved greater progress, if you had given her more chances. 如果你多给她点机会，她可能已经取得更大的成绩。 6.“should+have+done”意思是“本来应该做某事，而实际没做。”“shouldnt+have+done”表示本来不应该做某事，而实际做了。含有指责对方或自责的含意。 1). To
9、m, you are too lazy. The work should have been finished yesterday. 汤姆，你太懒惰了，这项工作本来应该昨天就做完的。 2). Look, Tom is crying. I shouldnt have been so harsh on him. 看，汤姆哭了，我本来不应该对他如此严厉。 7. “ought to+have+done”表示过去应该做而实际并没有做，译成“理应做”，往往表示遗憾。与“should+have+done”用法基本一样。例1. (2015北京)Cant you stay a little longer?Its
10、 getting late. I really _go now, My daughter is home alone.A .may B .can C . must D .dare 解析：考查情态动词辨析。句意：你不能再多待会儿吗?很晚了，我必须得走了。我女儿一个人在家。may可能，可以，也许；can能，会；must必须，必然要，必定会； dare敢，胆敢。结合句意，故选must。故可知本题答案。答案：C例2.(2015重庆) You_ be Carol. You havent changed a bit after all these years.A. must B. can C. will
11、D. shall解析：本题考查情态动词。句意：你肯定是卡罗，这些年你一点也没有变化。must表示对现在的肯定推测。 故选A。 答案：A 例3. (2015安徽安庆一中月考) If you were older I _ you to go there yesterday.A.will allow B. should allow C. would have allowed D. had allowed解析：从句是对现在的虚拟，而主句是对过去的虚拟，所以主句中要用“would/ should/ might/ could + have + 过去分词”由此可知本题答案。 答案：C例4. (2014北京海
12、淀二模)If I _the project earlier, I would be enjoying myself on the beach now. A. might finish B. finished C. had finished D. would have finished解析：句意：如果我能早此完成这个项目，我现在就在沙滩上享受了。本题混合条件句中虚拟语气。if引导的从句是对过去事实进行的虚拟。应用had finished。由此可知本题答案。答案：C例5. (2015北京海淀一模)What do you think of the Huawei P7?Terrific. I woul
13、d buy one if I _an iPhone 6 Plus last year. A. didnt buy B. dont buy C. hadnt bought D. havent bought解析：句意：你觉得华为P7怎么样？太棒了。如果去年我没有买iPhone 6 Plus的话，我就买一个华为P7。本题考查if引导的虚拟语气的用法。根据语境可知，此处为混合虚拟语气，if引导的条件从句是对过去发生的事情进行虚拟。根据语境可知本题答案。答案：C基础演练一单项选择。( )1.Marys sister looks very beautiful now. But she was very u
14、gly before she tidied up her appearance(整容). You _believe it! A. shouldnt B. mustnt C. wouldnt D. might not ( )2.Where is Mr. Smith? I cant find him anywhere. He _far, for his mobile phone is still here. A. mustnt have gone B. wouldnt have gone C. cant have gone D. shouldnt have gone ( )3.Why didnt John take part in the race yesterday? He _out of the race because of his serious injury. A. neednt have dropped B. should have dropped C. would have dropped D. must have dropped ( )4.
