英语专四虚拟语气汇总
专四虚拟语气
虚拟语气一、条件句中的虚拟语气1. 条件句中虚拟语气的形式从句中提出一种与客观现实不相符或根本不可能存在的条件，主句会产生的一种不可能获得的结果。
条件句中的虚拟语气根据不同的时间有三种不同的形式。
2. 条件句中的虚拟语气的举例(1) 将来时的条件句中的虚拟语气。
如：If he should go to Qing Hua University, he would make full use of his time. 如果他要上清华大学的话，他就会充分利用他的时间了。
(2) 现在时的条件句中的虚拟语气。
如：If he studied at this school, he would know you well. 如果他在这所学校学习的话，他会对你很熟悉。
(3) 过去时的条件句中的虚拟语气。
如：If I had seen the film, I would have told you about it. 我如果看过这场电影，我会把电影内容告诉你了。
3. 运用条件句中的虚拟语气时，须注意的几个问题(1) 当从句的主语为第三人称单数时，谓语动词若是系动词be时，可用was代替were。
但在倒装虚拟结构及if I were you, as it were中，只能用were。
如：Were I ten years younger, I would study abroad. 要是我还年轻十岁的话，我会去国外学习。
If I were you, I would try my best to grasp the chance. 要是我是你的话，我要尽力抓住这次机会。
(2) 有时，虚拟条件句中，主、从句的动作若不是同时发生时，须区别对待。
①从句的动作与过去事实相反，而主句的动作与现在或现在正在发生的事实不符。
如：If they had informed us, we would not come here now. 如果他们通知过我们的话，我们现在就不会来这里了。
英语四级语法 虚拟语气
虚拟语气一．一般虚拟条件句(1) 与现在事实相反——If I were you, I wouldn’t worry.——If I had the book at hand, I would read the passage to you.那么，虚拟语气现在时的句型为：从句：If + 主语＋动词过去式(be 变were) +…主句：主语＋would (should ,could ,might ) + 动词原形＋…(2) 与过去事实相反——If you had gone to last night’s games, you would have met him.——If the policeman had arrived earlier, he would have seen the accident.那么，虚拟语气过去时的结构是：从句：If＋主语＋过去完成时…主句：主语＋should (或would,could,might) + 现在完成时…(3) 与将来事实相反——If he should come tomorrow, I would give him the dictionary he needs.——If Mr. Li were to do the experiment tomorrow, he might read the instructions carefully.那么虚拟语气将来时的句型是：从句：If+主语＋should (或were to )+动词原形＋…主句：同虚拟语气现在时的主句结构。
练习：1.I f this report were more accurate, it __________ an invaluable document.A.wereB.had beenC.will beD.would be(D)2.I _______ in trouble if the police had stopped me.A.wereB.would have beenC.would beD.had been(B)3.W hat would you do if war _________ out.A.breaksB.could breakC.had broken outD. were to break(D)二、在if引导的虚拟条件句中，若有were, had, should，可省去if,将were, had, should提到主语前，形成倒装。
专四语法26条
1 虚拟语气: 动词原形 (1)that从句：（should+)动词原形 (2)条件从句：（should+)动词原形 (3)让步从句：（should+)动词原形 (4)目的从句：（shs necessary/my suggestion that • I suggest/recommend/propose that • If he be found guilty • Whatever be his defense • Though everyone desert you • Whether she be right or wrong • lest, for fear that, in order that, so that (should+动词原形）
• [than] • (4) There are more intelligent monkeys that Herbert.
2 比较结构: something of a N • As much/little of a N as • More/less of a N than
2 比较结构：more/less • many, much, few, little • as many (Adj) N as; as much (Adj) N as • (Adj) N as many as; (Adj) N as much as • I have more books than you. • *I have books more than you.
• 表“意外”的should: • It’s strange that he should have left without saying goodbye; He stepped into a cave and what he should see but a tigress with her baby tigers. • Who would have thought that things should come to such a tragic end.
专四虚拟语气总结(打印)
专四语法（虚拟语气）虚拟语气用来表示说话人的主观愿望或假想，所说的是一个条件，不一定是事实，或与事实相反。
条件句可分为两类，一类为真实条件句，一类为非真实条件句。
非真实条件句表示的是假设的或实际可能性不大的情况，故采用虚拟语气。
eg. If he comes, he will bring his violin.典型例题The volleyball match will be put off if it ___.A.will rainB. rainsC. rainedD. is rained答案B。
真实条件句主句为将来时，从句用一般现在时。
注意：1）在真实条件句中，主句不能用be going to表示将来，该用shall, will. (错) If you leave now, you are never going to regret it.(对) If you leave now, you will never regret it.2）表示真理时，主句谓语动词便不用shall (will) +动词原形，而直接用一般现在时的动词形式。
从句中提出一种与客观现实不相符或根本不可能存在的条件，主句会产生的一种不可能获得的结果。
条件句中的虚拟语气根据不同的时间有三种不同的形⏹If I had time, I would do it again.⏹If I had known of your arrival, I should have met you at the station.⏹If she had further considered the problem, she might have come to the correctconclusion.真题举例：1. All of us would have enjoyed the party much more if there _____ quite such a crowd people there.（00, 49）[C]A. weren’tB. hasn’t beenC. hadn’t beenD. w ouldn’t be2. If your car _____ during the first 12 months,take it to an authorized dealer.（98, 43）[B]A. shall needB. should needC. would needD. will need3. If there were no subjunctive mood, English _____ much easier to learn.(09, 52) [B]A. could have beenB. would beC. will beD. would have been4. _____ for the fact that she broke her leg, she might have passed the exam.(02, 60）[A]A. Had it not beenB. Hadn’t it beenC. Was it notD. Were it not5. If you explained the situation to your solicitor, he _____ able to advise you much better than I can. (05, 51) [A]A. would beB. will have beenC. wasD. were6. I was to have made a speech if _____. (97, 51) [C]A. I was not called awayB. nobody would have called me awayC. I had not been called awayD. nobody called me away当条件状语从句表示的行为和主句表示的行为所发生的时间不一致时，被称为：错综时间条件句，动词的形式要根据它所表示的时间做出相应的调整。
虚拟语气英语知识点总结
虚拟语气英语知识点总结一、虚拟语气的概念。
虚拟语气是一种特殊的动词形式，用来表示说话人所说的话不是一个事实，而是一种假设、愿望、怀疑、猜测或建议等。
二、虚拟语气在条件句中的用法。
1. 与现在事实相反的虚拟条件句。
- 结构：从句（If + 主语+ 动词的过去式（be动词一般用were）），主句（主语+ would/should/could/might+动词原形）。
- 例如：If I were you, I would study harder.（如果我是你，我会更努力学习。
实际上我不是你）2. 与过去事实相反的虚拟条件句。
- 结构：从句（If+主语+had+过去分词），主句（主语+would/should/could/might + have+过去分词）。
- 例如：If he had taken my advice, he would have passed the exam.（如果他听了我的建议，他就会通过考试了。
实际上他没听建议，也没通过考试）3. 与将来事实相反的虚拟条件句。
- 结构：从句（If+主语+动词的过去式/should+动词原形/were to+动词原形），主句（主语+would/should/could/might+动词原形）。
- 例如：If it rained tomorrow, we would stay at home.（如果明天下雨，我们就会待在家里。
明天是否下雨还不确定，但这是一种假设情况）- 或者If he should come tomorrow, I would tell him the news.（如果他明天来，我就会告诉他这个消息）- 以及If I were to see her tomorrow, I would give her the book.（如果我明天见到她，我就会把书给她）三、虚拟语气在宾语从句中的用法。
1. wish后的宾语从句。
- 表示与现在事实相反的愿望，从句谓语动词用过去式（be动词用were）。
专四常考语法结构3虚拟语气
If only the committee __ the regulations and put them into effect as soon as possible A approve B will approve C can approve D would approve D 注意：当if only后的句子表示与现在或将来事实 相反，该用动词过去式来表示虚拟语气，而选 项中又没有时，可以采用这种形式：would + 动词原形。
• I insist that we_______ (go) there by bus. • He susggested that we _________ (leave) early. • The judge ordered that the prisoner________ (be) sentenced to 30 days in jail.
• I wish I were as tall as you. 我 希望和你一样高。 He wished he hadn’t 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。 Wish sb / sth to do I 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.)
错综时态的虚拟语气
• 错综时态的虚拟语气即指主句和从句在 表达是与什么时态的事实相反上并不一 致（比如主句要表达与现在事实相反而 从句要表达与过去事实相反），这种情 况要采用“对号入座”的方法来处理， 即主从句结构分别采用与其表达时态对 应的结构。Eg.
四级语法虚拟语气
• It is( high) time…句型用虚拟语气! • It is high time that we were off. 是我们该 走的时候了。 • It is time that we went to bed. • It is time we should go to bed.= It is time for her to go to bed. • 在for fear that, in order that, so that, lest 引 导的目的状语从句用虚拟语气，谓语动 词用原形。
错综时间条件句
在错综时间条件句子中，虚拟条件从句和主句动 作发生不一致，因此，主句和从句的谓语动词 要根据各自所指的不同时间选用适当的虚拟语 气形式。
Eg. 1.If I hadn’t stood under the ladder to catch you when you fell, you now. A. couldn’t have smiled B. wouldn’t be smiling C. didn’t smile D. won’t smile 2. 如果我是你，我就不会错过昨晚那部电影。（现在— 过去）
虚拟语气用在suggest, order, demand 等后的宾语 从句中，谓语动词用原形 • 在propose, command, request, desire, insist, require, decide, promise, arrange, ask 要求， consent, determine, recommend, advise, intend, beg, resolve决意，argue, maintain主 张，expect希望，object, vote, urge, instruct, advocate, persuade, dictate, appoint, specify, persist等意念动词、祈使动词或态度动词 后的并与从句中用虚拟语气。
英语专四语法总结
1.主谓一致就近原则1.由并列结构或连词（either…or，neither…nor，not…but，not only…but also，or 等）连接的并列主语，谓语动词与靠近的那个名词或代词保持一致。
2. 在倒装句和there be句型中，谓语动词与后面的第一个主语保持一致。
例句：There is a book and some pens on the desk.桌子上有一本书和几支钢笔。
3. 在强调句中，连接代词又在句中作主语，这时它应与被强调的主语保持一致。
例句：It is Ma ry’s brother who was injured in the car accident. 是Mary的哥哥在车祸中受伤了。
意义一致原则1. 当主语与谓语动词之间插入along with，with，as well as，together with，no less than，besides，except，but，including等短语时，谓语动词不受这些插入语的干扰，依然和主语保持一致。
例句：I, along with my sister, am going to Shanghai next month. 我，还有我姐姐，打算下个月去上海。
2. 英语中有一类单、复数同型的词（people，means，sheep，deer，fish等），其单、复数取决于它在句中的含义。
例句：All of the people in the country have been prepared for the great reformation.这个国家的人都已经为大变革做好了准备。
3. 多数情况下，由“what”引导的名词性从句作主语时，其后的谓语动词通常用单数形式。
例句：What I want to say is just “ T ake care!”.我只想说：“多保重！”4. 当主语与all，none，any，some等不定代词、形容词连用时，应根据具体句意，来决定其后的谓语动词的单复数。
专四语法部分
1与现在事实相反
从句—v.过去式(be在一、三人称后可用was/were，通常用were较多)
2与过去事实相反
从句—v.过去完成式(had done)
3与将来事实相反，即将来不太可能发生
从句--情态v. (might) + v.原形
Eg. He talks as if hewerea scholar. (In fact, he is not a scholar.)
用在wish后的宾语从句中，表示不可实现的愿望。
主句通常为I wish,从句用下列形式：
1与现在事实相反,即目前未能实现的愿望
从句--v.过去式(be→were)
2与过去事实相反，即过去未能实现的愿望
从句--①had done(v.过去完成式)
②情态v.+ have done（动词的完成式）
3将来不太可能实现的愿望
I second Mr. Green’s motion that the meetingbe put offuntil next week.
2上述动词的形容词后的that主语从句也要求相同形式的虚拟语气。
advisable, desirable, preferable, urgent, …
It is advisable that you (should) go to see a doctor.
If Iwereyou, Ishould go and seethe doctor at once.
Icould have mether if Ihad comea few minutes earlier.
If shehadn’t got uplate, shewouldn’t have beenlate for school.
英语专业四级词汇语法辅导-虚拟语气、非谓语动词
It’s (high, about) time that 句型中that从句中要求用虚拟语气形式，即动词要用过去式。
虚拟语气的几个句型
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if it were not for…与现在事实相反， if it had not been for与过去事实相反，两个都相当于but for：
虚拟语气的几个句型
whether it (he) be …or…意为“不管（不论）是……还是……”，表示让步，为虚拟语气的一种表示方法，其省略结构为be it…or…, be he…or等，必须用倒装。例如：
Be he what he may, he should obey the rules.
虚拟语气的几个句型
虚拟语气的几个句型
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虚拟语气的几个句型
would rather +
动词过去式（与现在或将来事实相反） had + 过去分词（与过去事实相反）
do… (than do…) 宁愿…(而不…) sb. +
虚拟语气的几个句型
had hoped/thought引起的宾语从句中谓语动词形式为would+动词原形，表示一种过去未实现的愿望或令人失望的事。 His father had hoped that his son would go to business with him, but his son became an artist later.
虚拟语气常用句型
虚拟语气常用句型
NOTE: 当suggest意为“暗示”，insist意为“坚持认为（一个事实）”时，其后的宾语从句中不用虚拟语气。例如： Her face suggested (暗示) that she was ill. So I suggested (建议) that she (should) be sent to the hospital immediately. He insisted that he was right. 她坚持认为自己是对的。
四级必用虚拟语气非常完整版
虚拟语气学习虚拟语气的三个必知英语一共有三种语气形式，所有的祈使句都是祈使语气，其他非祈使句的句子或者属于陈述语气，或者属于虚拟语气。
学习虚拟语气必须明确了解以下三点：1、英语的所谓“虚拟语气”，从用途上区别有三种：一种用来表达与实际情况相反的虚构假设，一种用来表达“祈使愿望”的口气，另一种满足特殊的句式需要。
虚拟语气：（1）用来表示说话人的主观愿望、请求、意图、建议、怀疑、假设等；（2）可能性很小或不可能成为客观事实的情况，常用于非真实条件句中 虚拟语气并不全是在表达虚构的情况，理解这一点非常重要。
2、虚拟语气从句式表现上有三种：表达与实际情况相反的虚构假设用were 式虚拟，表达“祈使愿望”的口气be 式虚拟，在特殊句式中的照句式要求而定。
3、学习虚拟语气，其目的不在于单纯解决语法问题，更不能停留在应试的层面上。
掌握虚拟语气的用法对英语的阅读理解非常重要，尤其是进入大学以后，这一点更为重要。
一、虚拟条件句：非真实条件句虚拟条件句因为有虚拟语气，所以条件句中的条件是不可能的，主句的结论也是想象的，非真实的，不可能的。
1. If it rains tomorrow, our trip will be put off.如果明天下雨，我们的旅行就延后（真实条件句）2. If he hadn ’t hurt his legs yesterday, he would go with us now.要是他昨天没有伤到腿，现在他就会跟我们一起去。
（虚拟）虚拟条件句的基本形式1. If it _______ not for the fact that he is ill, I _______ him to do this right now.要不是他现在病了，我就让他现在去办这件事。
Were would ask2. If we _______ adequate preparations, the conference _______ so successful.如果我们不是做了充分的准备，这次会议就不会这么成功。
英语专业四级虚拟语气
▪ 主要手法
▪ 过去时态的虚拟
▪ 主要出现在if, if only, as if
▪
wish, would rather
▪
it is time that
考点一：用于非真实条件句(过去式
1 与现在事实相反：if 条件句中用一般过去时，主句用 should/would/could/might+动词原形
考点六：用于it is (about / high/ getting) time后that从句
I’d rather you ____ by train because the weather forecast said there would be heavy snow tomorrow. ▪ A. went B. should go C. will go D. go
▪ 我宁愿你乘火车去…， would rather 后接虚拟 语气的从句，用一般过去时。答案 A
虚拟语气的类型（三种）
▪ 原型虚拟 （Be） ▪ Were型虚拟（可以用was,也是过去式） ▪ 过去时态虚拟 ▪ Be he rich or poor, I will marry him all the same. ▪ If only I were a millionaire. (现在状态相反） ▪ I would rather you had come to our April Fool’s
▪ 0652. If only I ____ play the guitar as well as you!
▪ A would ▪ 答案 B
B could C should D might
考点五 在would rater, would sooner, would just as soon 从句
专四常见虚拟总结
1.条件句的虚拟（if）比如：(1) 与过去事实相反If I had seen the film, I would have told you about it.(2) 与现在事实相反If he were free, he would help us.要是他有空的话，它会帮助我们的。
(3). 与将来事实相反If he were to come here, he would tell us about it.如果他要来的话，他会通知我们一声。
If he studied at this school, he would know you well.如果他在这所学校学习的话，它会对你很熟悉。
注意省略if的倒装形式，比如：If I had studied hard, I would have passed the exam.Had I studied hard, I would have passed the exam.2. 一些表示请求、要求、命令或建议等意义的动词所接的宾语从句advise, ask, demand, desire, decide, insist, order, propose, request, sugge st其虚拟语气的结构为：(should) + 原形动词。
如：The teacher advised that we should make good use of every minute her 老师劝我们要好好地利用在这儿的每一分钟。
The Party asked that we should serve the people with our heart and soul 党要求我们要全心全意地为人民服务注意suggest和insist这两个词，当insist的意思为：坚决认为，坚持说；suggest的意思为：表明，暗含，暗示等时，宾语从句不用虚拟语气。
如：Tom insisted that he hadn’t stolen the watch.汤姆坚持说他没有偷那块手表。
英语专四真题汇总之虚拟语气
英语专四真题汇总之虚拟语气Ⅰ.2004年54.＿＿if I had arrived yesterday without letting you know beforehand?A．Would you be surprised B. Were you surprisedC. Had you been surprisedD. would you have been surprised[A] 译文：如果昨天没有通知你我就来了，你会觉得奇怪吗？虚拟语气题。
从句表示与过去的事实相反的情况，但主语中含有未来发生的意思，而且是问对方现场的感受，所以动词形式应与表示现在的时间一致，故选A。
56.It is imperative that students ＿＿their term papers on time.A. hand inB. would hand inC. have to hand inD. handed in[A] 译文：学生必须按时上交他们的学期论文。
句中单词imperative是虚拟语气的一个标志，后面的主语从句中的谓语应该用should加动词原形或者直接用动词原形，故A正确。
Ⅱ.2005年51.If you explained the situation to your solicitor , he ＿＿able to adviseyou much better than I can.A. would beB. will have beenC. wasD. were[A]译文：如果你把情况说给你的律师，他的建议会比我给你的建议更好。
根据句意，从句用的是过去时态，主句要用过去将来时态，故A正确。
63.＿＿you ＿＿further problems with your printer, contact your dealer foradvice.A. If , hadB. Have, hadC. Should, haveD. In case, had[C]译文：如果你的打印机再有问题，请联系经销商获取建议。
四级语法细说虚拟语气
专业四级语法考点细说I.虚拟语气1.if条件句当中，主从句都使用相应的虚拟形式。
当if被省略时，从句当中的虚拟形式had, were, should要提到从句的主语前面，构成倒装。
例：♦Were I you, I would take an umbrella with me.♦Should I have time, I would call her.♦Had the damage been worse, the insurance company would have paid more.2.主从句的时间背景不一样。
或者所表示的是与过去事实相反的假设。
例：♦If I had hurried, I would be on the train now.♦We would have dropped by if we had had time.♦I wouldn’t have known what these were for if I hadn’t been told.3.It is (high, about, the) time that ........... "早该做某事而已经有些晚了”例：♦It’s high ti me that we finished all the tasks.♦It’s the time the children learned how to behave properly.4.if引导让步状语从句，从句当中可以用虚拟语气。
“即使，就算”。
还有表示让步的一些表达法much as "尽管，虽然”，granted that "即使”例：♦We won’t change out plan if the rumor be true.♦Much as I would have liked to, I couldn’t lend him the money because I simply didn’t have that much spare cash.♦Granted that you had been drunk, there is no excuse for you to do that.5.与将来相反的虚拟的三种形式。
英语四级高级语法讲解：虚拟语气
英语四级高级语法讲解：虚拟语气1.if 引导的虚拟语气2.倒装形式Were I you(=if I were you),I would get up early in the morning.Had you arrived at the station ten minutes earlier yesterday(=If you had arrived…),you could have caught the train.Should it rain(=If it should rain),the crops would be saved.It is time that ...Would rather that.....(1)I would rather he came tomorrow than today.(2)John would rather that she had not gone to the party yesterday evening.(3)I would rather everything hadn t happened in the past.“It is(was)+形容词(或过去分词)+that……”结构中的虚拟语气1.It is necessary that we(should 可省略,下同)have a walk now.2.It was necessary that we(should) make everything ready ahead of time.3.It is required that nobody(should) smoke here.4.It is important that every pupil(should) be able to understand the rule of school.练习1.He’ll be busy this afternoon.If he ___ free,he ___ to the cinema with you.A.were to be; might goB.am going to be; will goC.will be; might have goneD.is; will go2.When Edison died,it was proposed that the American people _____ all power in their homes,streets,and factories for several minutes in honor of this great man.A.turn offB.turned offC.would turn offD.had turned off3.Had I known her name,_____.A.or does she know mine?B.and where does she live?C.I would have invited her to lunchD.she would be beautiful4.I’d rather you ______ by train,because I cant bear the idea of your being in an airplane in such bad weather.A.would goB.should goC.wentD.had gone5.The victim ________(原来会有机会活下来) if he had been taken to hospital in time.would have a chance to survive(06.12翻译)6.The professor required that ________(我们交讨论报告)。
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1. If the earth suddenly _______ spinning, we would all fly off it.A. had stoppedB. stoppedC. has stoppedD. would stop2. It is highly desirable that a new president _______ for this college.A. appointedB. be appointedC. is appointedD. has been appointed3. It was proposed that the matter _______ discussed at the next meeting.A. will beB. wasC. isD. be4. He didn’t go to the party, but he does wish he _______ there.A. had beenB. has beenC. would have beenD. would be5. It was essential that the application forms _______ back before the deadline.A. must be sentB. would be sentC. be sentD. were sent6. My cat would not have bitten the toy fish _______ it was made of rubber.A. if she has knownB. if she knewC. she should have knownD. had she known7. That tree looked as if it _______ for a long time.A. hasn’t wateredB. didn’t waterC. hadn’t been wateredD. wasn’t watered8. It is necessary _______ the dictionary immediately.A. that he will returnB. that he returnedC. that he returnD. that he has to return9. You’re talking to me as if I _______ an expert.A. amB. wasC. have beenD. were10. “Mary wants to see you today.”“I would rather she _______ tomorrow than today.”A. comesB. cameC. should comeD. will come11. I t’s getting rather late. It’s time we _______.A. are goingB. wentC. goD. must go12. It was unkind of you to say that ；you really _______ done so.A. should notB. should not haveC. need notD. must not13. This experiment _______ last week.A. should be doneB. should have been doneC. should have doneD. should do14. If it had rained last night, the roads _______ wet now.A. would have beenB. wereC. must beD. would be15. _______ you were coming today, I’d have met you at the airport.A. Have I knownB. I have knownC. Had I knownD. I had known16. If the sun _______ tomorrow, what would we do?A. would not riseB. should not riseC. had not riseD. does not rise17. Without your help, we _______ so much.A. wouldn’t have achievedB. will not achieveC. didn’t achieveD. don t achieve18. Care must be taken in using this method lest overflow _______.A. should occurB. occursC. occurredD. will occur答案与解析1. B如果地球突然停止转动，我们都将飞离出去。
虚拟语气。
if 引导的假设性条件状语从句，表达与现在事实相反的假设情况时，从句动词结构使用过去式，主句动词使用would + V原形。
2. B一位新校长被任命来这所大学，这是最好不过的了。
虚拟语气。
It is + adj . + that...主语从句中，动词使用should + V原形，should 可以省略。
常用形容词有essential, necessary, desirable, incredible, important, imperative等。
3.D有人提议这个问题下次会议再讨论。
虚拟语气。
It is + V过去分词+ that...从句中，动词使用should + V原形，should 可以省略。
动词一般含有“建议、决定、要求、命令”之意。
4.A他没有去参加宴会，但是他着实希望他（那时）在那儿。
虚拟语气。
wish后的宾语从句中，表达与过去事实相反的愿望，谓语动词使用过去完成时。
5.C申请表在截止日期前送回去，这是非常必要的。
虚拟语气。
解析同2 。
6.D如果我的猫知道玩具鱼是由橡胶做成的话，她就不会抓咬它了。
虚拟语气。
if 引导的非真实性条件状语从句，表达与过去事实相反的假设情况时，从句动词结构使用过去完成时，主句动词使用would + have done。
7.C那棵树看上去好像已经很长时间没有浇水了。
虚拟语气。
as if在引导的方式状语从句中表示“仿佛，好像” ，如果表示与过去事实相反，对过去情况的推测，谓语动词则使用过去完成时。
8.C他要立即归还字典，这是极为必要的。
虚拟语气。
解析同2 。
9.D你（现在）同我说话（的样子）仿佛我是个专家。
虚拟语气。
as if在引导的方式状语从句中，表示“仿佛，好像”，如果表示与现在事实不符，对现在情况的推测，谓语动词则使用过去式，如果是be动词，则使用were。
10. B“玛丽今天想见你。
”“与其今天来，我宁愿她明天来。
”虚拟语气。
would rather后的从句中，如果表示与现在或将来事实不符的情况，谓语动词使用一般过去时。
11.B天色很晚了，我们该走了。
虚拟语气。
It is (about / high) time (that)后的从句中，表示早该做而未做的事，含“建议”的意味，谓语动词使用一般过去时。
12.B你说那些话太不友善了，你本不该那么做。
虚拟语气。
情态动词should not + have done结构表示“本不该……”。
13.B这项实验本该上周做的。
虚拟语气。
解析同12 。
情态动词should + have done结构表示“本该……”。
14.D如果昨晚下了雨，现在路上就会湿。
虚拟语气。
if 引导的错综时间的非真实性条件句，如果从句表示与过去事实相反的情况，主句表示与现在事实相反的情况，则从句动词使用过去完成时，主句动词使用would + V原形。
15.C如果我早知道你今天来，我就会去机场接你。
虚拟语气。
if 引导的非真实性条件状语从句，表达与过去事实相反的假设情况时，从句动词结构使用过去完成时，主句动词使用would + have done。
如果从句连词if省略，则呈倒装语序。
16.B万一明天太阳不升起，我们该怎么办？虚拟语气。
if 引导的非真实性条件状语从句，表达与将来事实相反的假设情况时，从句动词结构使用should +V原形或were to do ，主句动词使用would +V 原形。
17.A没有你的帮助，我们就不会取得如此多的成就。
虚拟语气。
有时假设的情况并不以条件从句的形式表现，而是通过一个介词短语、上下文或其他方式表现，此为含蓄条件句。
与过去情况不符，动词使用would+ have done。
18. A必须小心使用这种方法，以防溢流发生。
虚拟语气。
以lest ，for fear that和in case引导的状语从句中，谓语多使用should + V原形。