1、a.同现在事实相反的假设。句型 ： 条件从句主句 一般过去时should（ would） +动词原形If they were here, they would help you.b.表示于过去事实相反的假设。 条件从句主句过去完成时should（would） have+ 过去分词If she had worked harder, she would have succeeded.The rice would not have been burnt if you had been more careful.If my lawyer had been here last Saturday, he
2、would have prevented me from going. If he had come yesterday, I should / would have told him about it.含义：He did not come yesterday, so I did not tell him about it.If he had not been ill and missed many classes, he would have made greater progress. He was ill and missed many lessons, so he did not ma
3、ke greater progress.c.表示对将来的假想条件从句主句一般过去时should+ 动词原形were+ 不定式would + 动词原形should+ 动词原形If you succeeded, everything would be all right.If you should succeed, everything would be all right.If you were to succeed, everything would be all right. 3.混合条件句主句与从句的动作发生在不同的时间，这时主，从句谓语动词的虚拟语气形式因时间不同而不同，这叫做混合条件句
4、。If you had asked him yesterday, you would know what to do now.（从句与过去事实相反，主句与现在事实相反。）If it had rained last night （过去）, it would be very cold today （现在）. 4.虚拟条件句的倒装虚拟条件句的从句部分如果含有were, should, 或had, 可将if省略，再把were, should或had 移到从句句首，实行倒装。Were they here now, they could help us.=If they were here now, th
5、ey could help us.Had you come earlier, you would have met him=If you had come earlier, you would have met him.Should it rain, the crops would be saved.=Were it to rain, the crops would be saved.在虚拟语气的从句中，动词be的过去时态一律用were，不用was， 即在从句中be用were代替。If I were you, I would go to look for him.如果我是你，就会去找他。If
6、he were here, everything would be all right. 如果他在这儿，一切都会好的。_ to do the work, I should do it some other day.A. If were IB. I wereC. Were ID. Was I 答案C. 在虚拟条件状语中如果有were, should, had这三个词，通常将if省略，主语提前, 变成 were, should, had +主语的形式。但要注意，在虚拟条件状语从句中，省略连词的倒装形式的句首不能用动词的缩略形式。如我们可说 Were I not to do., 而不能说 Weren
7、t I to do. 5特殊的虚拟语气词：should1） It is demanded / necessary / a pity + that结构中的主语从句的谓语动词要用should 加动词原形， should 可省略。（1）suggestedIt is（2）importantthat+ （should） do（3） a pity（1）suggested, ordered, proposed, required,demanded, requested, insisted； + （should） do （2）important, necessary, natural, strangea pi
8、ty,a shame,no wonder（3）It is suggested that we （should） hold a meeting next week.It is necessary that he （should） come to our meeting tomorrow.2）在宾语从句中的应用在表示命令、建议、要求等一类动词后面的从句中。order, suggest, propose, require, demand, request, insist, command, insist + （should） do I suggest that we （should） hold a
9、meeting next week.He insisted that he （should ） be sent there. 如suggest, insist不表示建议 或坚持要某人做某事时，即它们用于其本意暗示、表明、坚持认为时，宾语从句用陈述语气。The guard at gate insisted that everybody obey the rules.判断改错:（错）You pale face suggests that you （should） be ill. （对）Your pale face suggests that you are ill.（错）I insisted th
10、at you （ should） be wrong.（对）I insisted that you were wrong.3）在表语从句，同位语从句中的应用在suggestion, proposal, idea, plan, order, advice等名词后面的表语从句、同位语从句中要用虚拟语气，即（should）+动词原形。My idea is that we （should） get more people to attend the conference.I make a proposal that we （should） hold a meeting next week. 6.wish
11、的用法1）用于wish后面的从句，表示与事实相反的情况，或表示将来不太可能实现的愿望。其宾语从句的动词形式为：真实状况wish后从句动作先于主句动词动作过去时过去完成时（be的过去式为 were）从句动作与主句动作同时发生 现在时过去时（had + 过去分词）将来不大可能实现的愿望将来时would/could +动词原形I wish I were as tall as you.我希望和你一样高。He wished he hadnt said that. 他希望他没讲那样的话。I wish it would rain tomorrow. 我希望明天下雨就好了。2）Wish to do表达法。Wi
12、sh sb / sth to doI wish to see the manager. = I want to see the manager.I wish the manager to be informed at once. （= I want the manager to be informed at once.） 7.比较if only与only ifonly if表示只有；if only则表示如果就好了。If only也可用于陈述语气。I wake up only if the alarm clock rings. 只有闹钟响了，我才会醒。If only the alarm cloc
13、k had rung.当时闹钟响了，就好了。If only he comes early.但愿他早点回来。8.It is （high） time thatIt is （high） time that 后面的从句谓语动词要用过去式或用should加动词原形，但should不可省略。It is time that the children went to bed.It is high time that the children should go to bed. 9 need 不必做和本不该做didnt need to do表示： 过去不必做某事, 事实上也没做。.neednt have don
14、e表示： 过去不必做某事, 但事实上做了。John went to the station with the car to meet Mary, so she didnt need to walk back home. 约翰开车去车站接玛丽，所以她不必步行回家了。John went to the station with the car to meet Mary, so she neednt have walked back home. 约翰开车去车站接玛丽，所以她本不必步行回家了。（Mary步行回家，没有遇上John的车。There was plenty of time. She _. A.
15、 mustnt have hurriedB. couldnt have hurriedC. must not hurryD. neednt have hurried答案D。neednt have done. 意为本不必，即已经做了某事，而时实际上不必要。Mustnt have done 用法不正确，对过去发生的事情进行否定性推断应为couldnt have done, 不可能已经 must not do 不可以（用于一般现在时）。语气是一种动词形式，用以表示说话者的意图或态度。虚拟语气表示说话者的主观愿望、假想和建议等，所说的话有的与现在事实相反，或与过去事实相反，或与将来事实相反或与将来事实
16、可能相反。所以虚拟语气总是与假设条件句用在一起。除了if条件句外，还有几种常用的条件句，短语也可表示条件。此外，上下文也能创造虚拟的语言环境。但有时条件从句与结果主句可能发生时间不一致，有时虚拟语气会出现倒装情况。除了与条件句在一起使用的主句用虚拟语气外，有些宾语从句或表语从句也有用虚拟语气的情况。I虚拟语气的形式与基本用法 一、虚拟语气的形式 虚拟（条件）语气中，主句与从句中谓语动词的形式可分为下面四类 假设类型 条件从句谓语动词形式 主语谓语与现在事实相反 动词的过去式（be用were而不用was） would（第一人称可用should）+动词原形 与过去事实相反 had+ -ED分词 w
17、ould（第一人称可用should）+have + -ED分词 与将来事实相反 were to + 动词原形 would（第一人称可用should）+动词原形 与将来事实可能相反 should + 动词原形 二、虚拟语气的基本用法1. 与现在的事实相反1） What type of automobile would you buy ？A if you have free choice to choose the cars available todayB if you are free to choose among all the cars available todayC if all c
18、ars available were free to be chosen by youD if you were free to choose among all the cars available today2. 与过去的事实相反（有时主句中的should have done表示责备或后悔）2） he would have come to class. A If Mike is able to finish his homeworkB Would Mike be able to finish his homeworkC If Mike could finish his homeworkD
19、If Mike had been able to finish his homework 3） If the United States had not entered the Second World War，probably the 1940 unemployment rate of 14 still further. A would riseB would risenC would have risenD had risen 4） Top grade A diamonds had not B increased so sharply C in value in the late seve
20、nties D if one company had not controlled almost all of the worlds supply. 3. 与将来的事实相反 5） The report would be A released last January if new developments had not B made it necessary to revise all conclusions drawn from C the first series of D experiments. 6） It is said Tom will go to an appointment
21、tommorrow. If he were to come tomorrow, I ask him to go to your place. A willB wouldC shallD might 7） If you to see Mary，what would you tell her?A areB will be goingC mustD were 4. 与将来的事实可能相反 （1） If it should rain tomorrow, I would stay at home. 要是万一 明天下雨，我就呆在家里不出去。 事实上 现在天气很好，明天下雨的可能性应该不大，不过也说不准。（2
22、） If I should see her next Monday, I would tell her about it. 如果下周一我能见到她的话我就把这件事告诉她。三、例题解析 1） D为正确答案。2） D为正确答案。3） C为正确答案。4） B错。改为would have not。5） A错。改为would have been。6） B为正确答案。7） D为正确答案。II 虚拟语气的特殊表现形式 一、表示“好像”：除了if条件从句外，由as if和as though等引导的状语从句表示方式时，意思是“好像”,这时从句中的谓语动词应用虚拟语气。其动词形式用过去时（be用were的形式）表示
23、所说的与现在的事实相反；用过去完成时表示所说的与过去的事实相反1） Violetta has a curious A expression on B her face as though she was smiling C about something that amused her D .二、特殊连词的需要：lest, for fear that和in case引起的从句（这时谓语多用should加动词原形）We dare not play jokes on Mr. Wang lest he should become angry. （我们不敢跟王先生开玩笑，恐怕他生气。） He hurr
24、ied on, lest he should drop out in the forced match. （他加紧步伐，生怕在急行军中掉队。Every attention must be paid to him lest he （should） feel that he is inferior to my other guests. （我对他特别关照，唯恐他感觉到比我的其他客人低人一等。Hes working hard for fear that he should fail in the exam. （他加紧学习唯恐考试不及格。三、介词短语表示虚拟： 有时假设的情况并不以条件从句表示出来，而
25、是通过一个介词短语来表示，或通过上下文或其他方式表示出来。如 but for, but that, in case of, otherwise, supposing, under more favourable condition, without 等表示让步假设 He worked very hard; otherwise he might have failed. （他刻苦工作，不然他就失败了。We could have done better under more favorable conditions.（假设我们有更有利条件，我们还会做得更好。2） But for his help，
26、I . A should not have succeededB had not succeededC did not succeedD have not succeeded 3） The complex society of a modern A civilization would be B impossible not having C the art of writing D . 4） But that he came to help me, I . A could not have succeededB did not succeedC could not succeedD cant
27、 but succeed 四、虚拟错综条件句：上面几种假设类型中，主句与从句的谓语动词形式应前后呼应。但是，如果主句与从句的动作发生的时间不一致，谓语动词形式应做适当调整 If I had a bike（now）, I would have lent it to you yesterday. 假如我有自行车，昨天早就借给你了。（主句与过去事实相反，从句与现在事实相反。） I am very sorry if I had done anything wrong to you, but I am sure that it was unintentional.（如果我当时对你作错了什么事，我向你表示抱歉。但我敢保证我不是故意的。5） If the United States had built more homes for poor people in 1955，the housing problems now in some parts o
