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考研英语语法解读虚拟语气篇1
(一)并不是if引导的条件从句都是虚拟语气。如果if从句所指的事很有可能发生，那么这是真实条件句；反之，则是虚拟条件句
A. If you study hard, you"ll surely pass the examination. (真实条件句)
B. If I were a bird, I could fly freely in the sky. (虚拟条件句)
(二)虚拟语气中，有时条件从句和主句的时态可以不一致，这种句子叫做混合条件句，也叫错综时间条件句。这种句子的形式要根据表示的时间来调整
A. If it had not been for me, you would not be free.
B. If you had spoken to him yesterday, you would know what to do now.
C. “If I had missed, ”said William Tell, “and had shot too low, I was going to use this arrow on you. ”
(三)有时虚拟条件不用条件从句，而用介词短语来表示
A. They would not be able to live without him.
B. He would have failed but for his teacher"s timely advice.
C. I had my hair cut off and sold it because I couldn"t have lived through Christmas without giving you a present.
D. If only you had worked with greater care!
(四)假设的情况有时可以通过上下文或其他方式表现出来
A. He would have given you more help, but he was so busy.
B. I was ill that day. Otherwise I would have taken part in the parade.
C. He raised himself completely, obliging me to rise too, or I could not have supported him.
D. Einstein cared little for money, though he could have been very rich.
(五)如果条件从句的谓语动词含有连系动词were或助动词had或should, 可将if省略，而把were, had或should移到主语之前，构成倒装句形式
If they were here now, they could help us. (自然语序)
A.
Were they here now, they could help us. (倒装句)
If you had come earlier, you would have met him. (自然语序)
B.
Had you come earlier, you would have met him. (倒装句)
If he should join them in their discussion, they would be happy. (自然语序)
C.
Should he join them in their discussion, they would be happy. (倒装句)
The ship would have sunk with all on board if it had not been for the captain. (自然语序)
D.
The ship would have sunk with all on board had it not been for the captain. (倒装句)
(六)虚拟语气的一些其他用法
(1)在动词wish后的宾语从句中谓语动词用过去式，表示现在或将来的愿望；用过去完成式，表示过去的愿望。
A. I wish I knew the answer.
B. I wish that the time had not passed so fast!
(2)would rather后的从句中也用以上的结构。
A. I would rather they came tomorrow.
B. I would rather you had gone there too.
(3)由as if或as though引导的状语从句，也用以上的结构。
A. She loves the child as if he were her own.
B. “How wild his white hair looked-as if it had been electrified. ”
(4)在suggest, order, demand, propose, command, request, insist等后面的宾语从句，谓语动词用should+ 动词原形(should可省略)。
A. They requested that he (should) go at once.
B. He ordered that all (should) take part in the work.
(5)与下列词有关的表语从句、同位语从句也用以上的结构。
suggestion(proposal), order(decision), request(demand), plan, idea, a shame, a pity, no wonder
A. My idea is that we (should) win him over.
(6)在It is important(necessary, strange, natural, wonderful)that后以及It is suggested(requested, proposed, arranged, desired, ordered, insisted)that后从句中亦用以上的结构。
A. It is necessary that everyone should be there in time.
B. It is suggested that she should sing a song.
(7)在It is (high/about) time that从句中，谓语动词用一般过去式表示将来。
A. It is time we went to bed.
B. It"s about time you began your work.
(8)由in order that, so that引导的状语从句用may或might加动词原形，而so that引导的状语从句也可用can或could加动词原形
A. The emperor ordered that the weavers should be given some gold in order that they might begin their work at once.
B. The teacher spoke slowly so that the students could(might)hear clearly.
(七)suggest表示“建议，提议”时，用虚拟语气；作“认为，提出，暗示，使人想起”时，用陈述语气
A. I suggest he (should) bring his friends in. (虚拟语气)
B. On the boy"s pale face there was a half smile that seemed to suggest that he was happy to have given his life for his country. (陈述语气)
C. I suggest that you had an ulterior motive in doing this(陈述语气)
(八)insist表示“坚持要”或“一定要(某人做某事)”时，用虚拟语气；作“坚持认为，坚决主张、坚持说(某人的观点)”时，用陈述语气
A. They insisted that he (should) obey the rules. (虚拟语气)
B. She insisted that she needed no help. (陈述语气)
C. He insists that Shanghai is the largest city in China. (陈述语气)
(九)should have done表示应该做的事没做；shouldn"t have done表示不该做的事做了；need have done表示必须做的事没做；needn"t have done表示不必做的事做了。这些也都是虚拟语气
A. “It"s our own fault, ”I thought bitterly. “We should have cut away the jungle brush. ”
B. How I regretted the hours wasted in the woods and fields, the days when I had played and should have studied!
C. You needn"t have spent so much time on the problem; it is not worth doing at all.
考研英语语法解读虚拟语气篇2
虚拟语气是一种特殊的动词形式，表示所说的话不是一个事实，而只是一种假设，愿望，建议，怀疑，猜测或不大可能实现的空想。
I.虚拟语气用在条件状语从句中
虚拟语气用在条件状语从句中，通常从句由连词if 引导。
1.与现在事实相反的虚拟条件句
条件状语从句主句
If +主语 +动词过去式主语+ would, should, could, might+原形动词
(be的过去式用were)
例如：
If I feared death, I wouldn"t be a communist.
(刘胡兰)怕死就不做共产党员。
If there were no air, we couldn"t live.
如果没有空气，我们就不能生活。
Example:
I would ask George to lend us the money if I ______ him.
A. had known B. knew C. have known D. know
I _____ it to him if I thought he would understand.
A. shall explain B. will explain C. would explain D. explain
2.与过去事实相反的虚拟条件句
构成
条件状语从句主句
If + 主语 + 动词过去完成式主语 + would, should, could, might+have + 过去分词
例如：
If you had come a few minutes earlier, you would have met him.
如果你早来几分钟，你就会碰上他。
If there had been no air in the tube, the result of the experiment would have been more accurate.
如果试管中没有空气，实验结果就会更精确。
Example:
If you hadn"t gone with Tom to the party last night, _______.
A. you would meet John already
B. you won"t have missed John
C. you will have met John
D. you would have met John
3.与将来事实相反的虚拟条件句
构成
条件状语从句主句
If + 主语+ should +原形动词主语+would,should,could,might或were+不定式+原形动词
例如：
If he were to come tomorrow, things would be easier.
假如他明天会来，事情就容易办了。
If the sand should be broken up, it would give out much energy.
如果沙子能被分解，它会释放出大量的能量。
注：在表示与将来事实相反的虚拟条件句中，从句中的should有时可以省略。如：
If he make the design, he might do it in some other way.
要是他来搞这个设计，他可能用另外的方法设计。
Example:
If the sea ____ to rise 50 feet, India would become an island.
A. will B. is C. was D. were
If you ____ to see Mary, what would you tell her?
A. are B. will be going C. must D. were
We might still catch the train if we ___.
A. make hurry B. haste
C. make haste D. hastily
4.错综时间的虚拟语气
在一些含有虚拟语气的句子中，如果主句与从句的谓语表示不同的时间，虚拟语气可有不同形式，即主句与从句各自按自己的时间构成虚拟形式。例如：
If I had met him before, I could recognize him.要是我以前遇见过他，我就能认出他了。
(从句表示与过去事实相反，主句表示与现在或将来事实相反)
If we were driving at a speed of 100 Li an hour, we would have arrived there 2 hours ago. 如果我们的行车速度每小时100里，两小时以前我们就会到达那里了。
(从句与现在事实相反，主句与过去事实相反)
Example:
If you _____ that late movie last night, you wouldn"t be sleepy.
A. haven"t watched
B. didn"t watch
C. hadn"t watched
D. wouldn"t have watched
5.省略连词if
在条件状语从句中，如果有were, should, had，可以把连词if 省去，把 were, should, had 放在句首，构成条件意义。例如：
Should it rain tomorrow, what would you do? 万一明天下雨，你怎么办?
Were there no friction, we could not walk. 要是没有摩擦力，我们就不能行走。
Had we known about the new method, we should have applied it earlier.
如果我们过去知道这种新方法，我们早就应用了。
Example:
Had Alice been more hardworking, she _______.
A. had not failed B. would not fail
C. could not be failed D. would not have failed
_______ today, he would get there by Friday.
A. Would he leave B. Was he leaving
C. Were he to leave D. If he leaves
______ difficulties, we would be successful.
A. Should we overcome B. Would we overcome
C. Might we overcome D. Could we overcome
6.虚拟结构中省略主句或从句
虚拟结构中有时可省去主句或从句，并不影响意义的完整。
(1)省去条件从句
That would be fine. 那太好了。(省去了if you would come 或类似条件)
I wouldn"t pass up the chance to visit China. 我不会放弃访问中国的机会。
We might have produced more coal. 我们可能生产出更多煤炭。
注：省略条件句，在试题中很少见到。
(2)省去主句，常用以表示愿望。从句谓语多用过去时或过去完成时。
If only she were here. 假如她在这儿该多好啊!
If only he lived! 假如他活着该多好啊!
If only I had known it before. 如果我早先知道这件事，那就好了。
Example:
If only it _____! but it is too late.
A. is avoided B. has avoided
C. could be avoided D. can be avoided
If only everything _____ out as we wanted it to in life!
A. is working B. worked
C. works D. has worked
考研英语语法解读虚拟语气篇3
解读虚拟语气
虚拟语气(Subjunctive Mood)是动词的一种特殊形式，用来表达说话人的愿望、请求、意图、建议、惊奇、设想等。虚拟语气这一语法项目几乎是四、六级必考的内容，也是各类英语考试中心测试的重点之一，考生应该熟练掌握。下面从五个方面介绍虚拟语气的用法。第一部分：语气的定义和种类
第二部分：简单句中的虚拟语气
第三部分：名词性从句中的虚拟语气
第四部分：条件句中的虚拟语气
第五部分：其他几种情况下的虚拟语气
第一部分：语气的定义和种类
1 语气(mood)
语气是动词的一种形式，表示说话人对某一行为或事情的看法和态度。
2 语气的种类
⑴、陈述语气：表示动作或状态是现实的、确定的或符合事实的"，用于陈述句、疑问句和某些感叹句。如：
①There are two sides to every question.每个问题都有两个方面。
②Were you busy all day yesterday? 昨天一整天你都很忙吗？
③How good a teacher she is! 她是多好的一位老师啊！
⑵、祈使语气：表示说话人对对方的请求或命令。如：
①Never be late again!再也不要迟到了。
②Don’t forget to turn off the light.别忘了关灯。
⑶、虚拟语气：表示动作或状态不是客观存在的事实，而是说话人的主观愿望、假设或推测等。如：
①If I were a bird, I could fly in the air.如果我是一只小鸟，我就能在空中飞行。
②I wish I could pass the examination.我希望我能通过考试。
③May you succeed!祝您成功！
虚拟语气在语法里算得上是个难点。让我们就从最简单的开始吧。
第二部分：简单句中的虚拟语气
一、情态动词的过去式用于现在时态时，表示说话人的谦虚、客气、有礼貌、或委婉的语气，常用于日常会话中。如：
⑴.Would you be kind enough to show me the way to the post office?请你告诉我去邮局的路好吗？
⑵.It would be better for you not to stay up too late.你最好别熬夜到很晚。
二、表祝愿。
1、常用“may+动词原形”表示祝愿，但愿，此时may须置于句首（多用于正式文体中）。
⑴、May good luck be yours!祝你好运！
⑵、May you be happy!祝你快乐！
⑶、May you do even better!祝你取得更大成就！
⑷、May you have a good time. 祝愿你玩的痛快。
⑸、May the friendship between us last long. 祝愿我们的友情天长地久。
⑹、May you be happy. (注意那个be ) 祝你幸福。
（7）May the world be filled with love! 让世界充满爱！
2、用动词原形。例如：
(1).Long live the people! 人民万岁！
(2).“God bless you,”said the priest.牧师说：“愿上帝保佑你！”
(3).Have a good journey! 祝愿你旅途愉快！
三、表示强烈愿望。（该类型虚拟语气谓语仅用动词原形，第三人称单数也不加“s”）
(1).God save me．
(2).Heaven help us．
四、表命令
1.命令虚拟语气只能用在第二人称(you)，而且通常省略主语(也就是you)。
2.句子尾通常加上感叹号：！
3.虚拟语气动词用一般现在时态(Simple Present)，如：work, be , go
4.否定形式的命令语气，可用助动词do，加上not。
(1). Work !
(2). Work harder !
(3). Be more alert ! (虚拟语气动词Be)
(4). You go out !
(5). Do not work so hard. (do not 表示否定的虚拟语气)
(6). Don"t be afraid. (口语中常用don"t 代替do not)
五、在一些习惯表达中。如：
(1).You’d better set off now.你最好现在就出发。
(2).I’d rather not tell you the secret.我情愿不告诉你这个秘密。
第三部分：名词性从句中的虚拟语气
第一节：宾语从句(Subordinate Clasue)中的虚拟语气
一、在动词wish后的宾语从句中的虚拟语气
在动词wish后的宾语从句中的虚拟语气，常省去宾语从句的引导词that。
一）、对现在情况的虚拟（与现在的事实相反）：
从句用过去式或过去进行式(时间上是同时的)。其句子结构为：宾语从句的谓语be和were(was)，实义动词用过去式。例：
1. I wish (that可省略,下同)I knew the answer to the question.(wish, 动词过去式knew)我希望知道这个答案。(事实上是不知道)
2. I wish it were spring in my hometown all the year around.(wish, were)但愿我的家乡四季如春。(事实上不可能)
3. I wish I were a bird.(wish, were)但愿我是只小鸟。(事实上不可能)
4. When she was at the party,she wished she were at home.(wished,过去虚拟动词were)(事实上并不在家)
5. Now that he is in China, he wishes he understood Chinese.(wishes,过去虚拟动词understood)
现在他在中国，他希望能懂得中文。(事实上并不懂)
6. When we begin the trip, they will wish they were with us.(will wish,过去虚拟动词were)(事实上并不和我们在一起)
二）、对过去情况的虚拟（和过去的事实相反）：
用wish表示对过去事情的遗憾。其句子结构为：宾语从句的谓语用过去完成时，或would, could, might+现在完成时。例：
1. I wish (that可省略，下同)I hadn"t wasted so much time.
我后悔不该浪费这么多时间。(事实上已浪费了)
2. He wishes he hadn"t lost the chance.
他真希望没有失去机会。(其实已失去)
3. We wished he had spoken to us.
(wished，had + spoken)(事实上他并没同我们讲)
4. I wish you had called earlier.
(wish, had + called)(事实上已迟了)
5. They will wish they had listened to us sooner.
(will wish,had + listened)(事实上并不如此)
例题分析：I wish I ______ longer this morning, but I had to get up and come to class.
A. could have slept B. slept C. might have slept D. have slept
动词wish后面接从句，表达不可能实现或与事实相反的情况时，谓语动词要用虚拟语气，即用过去式（表示现在发生的动作）或过去完成式（表示过去发生的动作）。本题后半句谓语动词have用的是过去时had to get up and come, 所以前面要用过去完成时表示过去发生的动作。所以, 选项A)could have slept是答案
三）、对将来情况的虚拟(表示将来的主观愿望)：
从句动词“would/should/could/might + 动词原形”(时间上较后)(请注意：主句和从句的主语不相同)。用wish表示对将来事情的愿望。例：
1. I wish it would stop raining.(虚拟动词would+动词原形stop)
我希望雨能停止。(事实上雨还在下着呢)
2. I wish you would be quiet.(would + be)
我希望你安静一些。(事实上那家伙还在吵着呢)
3. You wished she would arrive the next day.(would + arrive)
你希望她第二天会到。(事实上她还没到)
4. I wish she would change her mind.(would + change)
我希望她会改变主意。(呵呵，女孩子可没那么容易就改变主意喔)
5. He will wish we would join him the following week.(would + join)
(只是希望我们和他在一起，实际上还没在一起)
四）、注意：
1.如果将wish改为过去式wished, 其后that 从句中的动词形式不变。例如：
I wished I hadn"t spent so much money. 我要是那时没有花掉那么多钱就好了。
2. 如果that 从句中用would , 一般表示对现状不满或希望未来有所改变或请求
I wish he would answer my letter.
I wish prices would come down.
I wish you would help me.
I wish you would stop asking silly questions.
二、在表示建议、命令、要求、忠告等动词的后面的宾语从句中的虚拟语气
由于这些动词本身隐含说话者的主观意见，认为某事应该或不应该怎样，这些词语后面的“that”从句应用虚拟语气，且均以“should+动词原形”表示这种语气，但事实上“should”常被省略，故此从句中谓语动词用原形，常用的此类动词有：
表示“要求”的：ask, desire, request, demand, require, beg
表示“提议、劝告、建议”的：move, prpose, suggest, recommend, advise, vote
表示“决定、命令”的：decide, order
表示“主张”的：maintain, urge
表示“同意、坚持”的：consent, insist
例如：
1.The doctor suggested that he (should) try to lose his weight.
2.He insisted that we (should ) tell him the news.
3.When I suggested that he try shaving cream, he said, “The razor and water do the job. ”(当我建议他用刮胡膏时，他说“剃刀和水就行了”。)
4.He pursued various theories for several days until I suggested we take the toy apart to see how it did work. (他费了几天功夫寻找理论根据，直到我建议拆开看看它是如何转动
考研英语语法解读虚拟语气篇4
would rather后接句子时，句子谓语习惯上要用虚拟语气，具体用法为：
1.一般过去时表示现在或将来的愿望
I"d rather you went tomorrow (now). 我宁愿你明天(现在)去。
I"d rather you came next Saturday. 我宁愿你下星期六来。
I"d rather you were happy. 我愿你快乐。
I"d rather she sat next to me. 我宁愿她挨着我坐。
I"d rather Jack left on an earlier train. 我宁愿杰克乘前一班火车走。
You always go without me and l"d rather you didn"t. 你总是不带我去，我可不愿意你这样。
“Shall I open the window? ” “I"d rather you didn"t. ”“我要不要把窗子打开? ” “我看不要打开好。”
2. 用过去完成时表过去的愿望
I"d rather you hadn"t said it. 我真希望你没有这样说过。
I"d rather you hadn"t done that. 我宁愿你没这样做。
l"d rather you had been / hadn"t been present。我 (宁) 愿你当时在场 / 不在场。
l"d rather he had told / hadn"t told me about it 我 (宁) 愿他告诉了 / 未告诉我这件事。
Katie went by car and I"d rather she hadn"t. 凯蒂是坐汽车去的，我宁愿地不坐汽车去。
考研英语语法解读虚拟语气篇5
1) 概念
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。
2) 在条件句中的应用
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。
16.1 真实条件句
真实条件句用于陈述语气，假设的情况可能发生，其中 if 是如果的意思。
时态关系
句型： 条件从句 主句
一般现在时 shall/will + 动词原形
If he comes, he will bring his violin.
典型例题
The volleyball match will be put off if it ___.
A. will rain B. rains C. rained D. 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。
16.2 非真实条件句
1)时态：可以表示过去，现在和将来的情况。它的基本特点是时态退后。
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。
句型： 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 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.
含义： He was ill and missed many lessons, so he did not make greater progress.
c. 表示对将来的假想
句型： 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.
16.3 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。
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).
16.4 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, they 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.
注意：
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 he were here, everything would be all right.
如果他在这儿，一切都会好的。
典型例题
_____ to do the work, I should do it some other day.
A. If were I B. I were C. Were I D. 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"t I to do.
16.5 特殊的虚拟语气词：should
1) 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。
句型：
(1)suggested
It is (2)important that…+ (should) do
(3) a pity
(1)suggested, ordered, proposed, required, demanded, requested, insisted; + (should) do
(2)important, necessary, natural, strange
a pity, 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 meeting next week.
He insisted that he (should ) be sent there.
注意： 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 that 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.
16.6 wish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 现在时 过去时
(be的过去式为 were)
从句动作与主句动作同时发生 过去时 过去完成时
(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 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.)
16.7 比较if only与only if
only 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 clock had rung. 当时闹钟响了，就好了。
If only he comes early. 但愿他早点回来。
16.8 It is (high) time that
It 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.
16.9 need “不必做”和“本不该做”
didn"t need to do表示： 过去不必做某事, 事实上也没做。.
needn"t have done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 didn"t 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 needn"t 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。)
典型例题
There was plenty of time. She ___.
A. mustn"t have hurried B. couldn"t have hurried C. must not hurry D. needn"t have hurried
答案D。needn"t have done. 意为“本不必”，即已经做了某事，而时实际上不必要。
Mustn"t have done 用法不正确，对过去发生的事情进行否定性推断应为couldn"t have done, “不可能已经”。 must not do 不可以(用于一般现在时)。
虚拟语气英语语法知识点汇总