) 语法形式上要一致，即单复数形式与谓语要一致。2) 意义上要一致，即主语意义上的单复数要与谓语的单复数形式一致。3) 就近原则，即谓语动词的单复形式取决于最靠近它的词语，　　 一般来说，不可数名词用动词单数，可数名词复数用动词复数。例如：　There is much water in the thermos.　　 但当不可数名词前有表示数量的复数名词时，谓语动词用复数形式。例如：　Ten thousand tons of coal were produced last year.

15.1并列结构作主语时谓语用复数，例如：　Reading and writing are very important.读写很重要。　 注意：当主语由and连结时，如果它表示一个单一的概念，即指同一人或同一物时，谓语动词用单数，and此时连接的两个词前只有一个冠词。例如：　The iron and steel industry is very important to our life.钢铁工业对我们的生活有重要意义。典型例题　The League secretary and monitor ___ asked to make a speech at the meeting.

A. is　　B. was　C. are　D. were答案B.注： 先从时态上考虑。这是过去发生的事情应用过去时，先排除A.，C。本题易误选D，因为The League secretary and monitor好象是两个人，但仔细辨别，monitor前没有the，在英语中，当一人兼数职时只在第一个职务前加定冠词。后面的职务用and相连。这样本题主语为一个人，所以应选B。15.2主谓一致中的靠近原则1)当there be句型的主语是一系列事物时，谓语应与最邻近的主语保持一致。例如：　There is a pen, a knife and several books on the desk.桌上有一支笔、一把小刀和几本书。　There are twenty boy-students and twenty-three girl-students in the class.班上有二十个男孩，二十三个女孩。2)当either…or… 与neither…nor，连接两个主语时，谓语动词与最邻近的主语保持一致。如果句子是由here, there引导，而主语又不止一个时，谓语通常也和最邻近的主语一致。例如：　Either you or she is to go.不是你去，就是她去。　Here is a pen, a few envelops and some paper for you.给你笔、信封和纸。 15.3谓语动词与前面的主语一致当主语有with, together with, like, except, but, no less than, as well as等词组成的短语时，谓语动词与前面的主语部分一致。例如：　The teacher together with some students is visiting the factory.教师和一些学生在参观工厂。　He as well as I wants to go boating.他和我想去划船。15.4谓语需用单数1)代词each以及由every, some, no, any等构成的复合代词作主语时，或主语中含有each, every时,谓语需用单数。例如：　Each of us has a tape-recorder.我们每人都有录音机。　There is something wrong with my watch.我的表坏了。2)当主语是一本书或一条格言时，谓语动词常用单数。例如：　The Arabian Night is a book known to lovers of English.《天方夜谭》是英语爱好者熟悉的一本书。　3)表示金钱，时间，价格或度量衡的复合名词作主语时，通常把这些名词看作一个整体，谓语一般用单数。例如：　Three weeks was allowed for making the necessary preparations.用三个星期来做准备。　 Ten yuan is enough.十元够了。15.5指代意义决定谓语的单复数1)代词what, which, who, none, some, any, more, most, all等词的单复数由其指代的词的单复数决定。例如：All is right.　一切顺利。All are present.　人都到齐了。2)集体名词作主语时，谓语的数要根据主语的意思来决定。如family, audience, crew, crowd, class, company, committee等词后，谓语动词用复数形式时强调这个集体中的各个成员，用单数时强调该集体的整体。例如：　　His family isn\'t very large.他家成员不多。　　His family are music lovers.　他家个个都是音乐爱好者。　 但集合名词people, police, cattle, poultry等在任何情况下都用复数形式。例如：　　Are there any police around?附近有警察吗？3)有些名词，如variety, number, population, proportion, majority等有时看作单数，有时看作复数。例如：　A number of +名词复数+复数动词。　The number of +名词复数+单数动词。　A number of books have lent out.　The majority of the students like English.

15.6与后接名词或代词保持一致1)用half of, most of, none of, heaps of, lots of, plenty of等引起主语时，谓语动词通常与of后面的名词/代词保持一致。例如：　Most of his money is spent on books.他大部分的钱化在书上了。Most of the students are taking an active part in sports.大部分学生积极参与体育运动。2)用a portion of, a series of, a pile of, a panel of等引起主语时，谓语动词通常用单数。例如：A series of accidents has been reported.媒体报道了一连串的事故。A pile of lots was set beside the hearth.炉边有一堆木柴。3)如many a或more than one所修饰的短语作主语时，谓语动词多用单数形式。但由more than…of作主语时，动词应与其后的名词或代词保持一致。例如：　Many a person has read the novel.　许多人读过这本书。　More than 60 percent of the students are from the city.百分之六十多的学生来自这个城市。16.虚拟语气1)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。虚拟语气在条件句中应用比较多。2)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真实条件句用于陈述语气，假设的情况有可能发生。各种结构参见下表：句 型 条件从句 主句一般现在时shall/will +动词原形祈使句情态动词一般现在时例如：If he comes, he will bring his violin.如果他来，会带小提琴来的。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)虚拟语气可以表示过去，现在和将来的情况，时态的基本特点是时态往后推移。a.与现在事实相反的假设条件从句 主句 一般过去时(be用were)should(would)等+动词原形例如：If they were here, they would help you.如果他们在这儿，会帮助你的。含义：They are not here, they can’t help you.

b.与过去事实相反的假设条件从句 主句过去完成时should(would)等+ have+过去分词例如：If he had come yesterday, I should / would have told him about it.如果他昨天来的话，我会把这件事告诉他的。　 　 含义：He did not come yesterday, so I did not tell him about it.

c.表示对将来不大可能发生的事情的假想条件从句 主句一般过去时should/would等+动词原形were+不定式should+动词原形例如：If you succeeded, everything would be all right.如果你将来成功了，一切都会好的。　If you should succeed, everything would be all right.

If you were to succeed, everything would be all right.含义：You are not likely to succeed, everything will be what it is now.

16.3混合条件句有时，主句与从句的动作发生在不同的时间，主句从句谓语动词的虚拟语气形式因时间不同而不同，这种条件句叫做混合条件句。例如：　　If you had asked him yesterday, you would know what to do now.如果你昨天问过他，今天就知道做什么了。　 (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).如果昨晚下过雨，今天就会很冷了。16.4虚拟条件句的倒装　　虚拟条件句的从句部分含有were, should,或had时,可省略if，再把were, should或had移到从句的句首，实行倒装。例如：　Were they here now, they could help us. =If they were here now, they could help us.他们现在在的话，就会帮助我们了。　Had you come earlier, you would have met him. =If you had come earlier, you would have met him.你来得早一点，就碰到他了。　Should it rain, the crops would be saved. =Were it to rain, the crops would be saved.假如下雨，庄稼就有救了。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。例如：　　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should1)在主语从句中的应用It is demanded / necessary / a pity + that…等结构的主语从句，谓语动词用should加动词原形，should可省略。It is可用的词有三类that(should)do

suggested, ordered, required, proposed, demanded, requested, insisted等important, necessary, natural, imperative, strange等a pity, a shame, no wonder等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，像order, suggest, propose, require, demand, request, insist, command, insist +(should)do等。例如：　I suggest that we(should)hold a meeting next week.我建议下周召开个会议。　He insisted that he(should)be sent there.他要求被派到那儿去。　 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。　 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。例如：　　My idea is that we(should)get more people to attend the conference.我的想法是让更多的人来参加会议。　　I make a proposal that we(should)hold a meeting next week.我提了个建议，下周我们开个会。16.6 wish的用法1)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：主句 从句从句动作先于主句动词动作(be的过去式为were)现在时 过去时从句动作与主句动作同时发生(had +过去分词) 过去时 过去完成时将来不大可能实现的愿望 将来时would/could +动词原形例如：I wish I were as tall as you.　我希望和你一样高。　He wished he hadn\'t said that.他希望他没讲过那样的话。　I wish it would rain tomorrow.我希望明天下雨就好了。2)wish to do；wish sb / sth to do。例如：　I wish to see the manager. = I want to see the manager.我希望见一见经理。　I wish the manager to be informed at once.(= I want the manager to be informed at once.)我希望经理能马上得到消息。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。例如：　　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。例如：　It is time that the children went to bed.孩子们该睡觉了。　It is high time that the children should go to bed.

16.9 need \"不必做\"和\"本不必做\"　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。例如：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步行回家了，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)。17.名词性从句在句子中起名词作用的句子叫名词从句。名词从句的功能相当于名词词组,它在复合句中能担任主语、宾语、表语、同位语、介词宾语等，因此根据它在句中不同的语法功能，名词从句又可分别称为主语从句、宾语从句、表语从句和同位语从句。17.1引导名词性从句的连接词引导名词性从句的连接词可分为三类：　　 连接词：that, whether ,if(不充当从句的任何成分)　　 连接代词：what, whatever, who, whoever, whom, whose, which连接副词：when, where, how, why　　 不可省略的连词：　　　　1.介词后的连词　　　　2.引导主语从句和同位语从句的连词不可省略。例如：　　　　　That she was chosen made us very happy.她被选上了，我们很高兴。　　　　　We heard the news that our team had won.我们听到消息说我们队赢了。比较：whether与if均为\"是否\"的意思。 但在下列情况下，whether不能被if取代：1. whether引导主语从句并在句首2.引导表语从句3. whether从句作介词宾语4.从句后有\"or not\"　　 　　大部分连接词引导的主语从句都可以置于句末，用it充当形式主语。例如：　　It is not important who will go.谁去，这不重要。　　It is still unknown which team will win the match.到底谁赢呢，形势尚不明朗。17.2名词性that-从句1)由从属连词that引导的从句叫做名词性that-从句。That只起连接主句和从句的作用，在从句中不担任任何成分，本身也没有词义。名词性that-从句在句中能充当主语、宾语、表语、同位语和形容词宾语。例如：　 主语：That he is still alive is sheer luck.　 他还活着全靠运气。　 宾语：John said that he was leaving for London on Wednesday.　约翰说他星期三要到伦敦去。　 表语：The fact is that he has not been seen recently.事实是近来谁也没有见过他。同位语：The fact that he has not been seen recently disturbs everyone in his office.近来谁也没有见过他，这一情况令办公室所有的人不安。　 形容词宾语：I am glad that you are satisfied with your job.你对工作满意我感到很高兴。　2)That-从句作主语通常用it作先行词，而将that-从句置于句末。例如：　　 It is quite clear that the whole project is doomed to failure.　很清楚，整个计划注定要失败。　　It\'s a pity that you should have to leave.　你非走不可真是件憾事。　　 用it作形式主语的that-从句有以下四种不同的搭配关系：　a. It + be +形容词+ that-从句　　　It is necessary that…　　　 有必要……　　　It is important that…　　　 重要的是……　　　It is obvious that…　　　　 很明显……　b. It + be + -ed分词+ that-从句　　　It is believed that…　　　　　人们相信……　　　It is known to all that…　　　 从所周知……　　　It has been decided that…　　 已决定……　c. It + be +名词+ that-从句　　　It is common knowledge that…　 ……是常识　　　It is a surprise that…　　 令人惊奇的是……　　　It is a fact that…　　　　 事实是……　d. It +不及物动词+ that-分句　　　It appears that…　　　　　　似乎……　　　It happens that…　　　　　　碰巧……　　　It occurred to me that…　　 我突然想起……17.3名词性wh-从句1)由wh-词引导的名词从句叫做名词性wh-从句。Wh-词包括who, whom,. whose, whoever, what, whatever, which, whichever等连接代词和where, when, how, why等连接副词。Wh-从句的语法功能除了和that-从句一样外，还可充当介词宾语、宾语补语和间接宾语等。例如：主语：How the book will sell depends on its author.　书销售如何取决于作者本人。直接宾语：In one\'s own home one can do what one likes.　在自己家里可以随心所欲。间接宾语：The club will give whoever wins a prize.　获胜者俱乐部将颁奖。表语：My question is who will take over president of the Foundation.　我的问题是谁将接任该基金会主席职位。宾语补足语：She will name him whatever she wants to.她高兴给他起什么名字就取什么名字。同位语：　　I have no idea when he will return.　 我不知道他什么时候回来。形容词宾语：I\'m not sure why she refused their invitation.　我尚不能肯定她为什么拒绝他们的邀请。介词宾语：　That depends on where we shall go.那取决于我们去哪儿。2)Wh-从句作主语也常用先行词it做形式主语，而将wh-从句置于句末。例如：　It is not yet decided who will do that job.　 还没决定谁做这项工作。　It remains unknown when they are going to get married.　他们何时结婚依然不明。17.4 if, whether引导的名词从句1)yes-no型疑问从句　　从属连词if, whether引导的名词从句是由一般疑问句或选择疑问转化而来的，因此也分别被称为yes-no型疑问句从句和选择型疑问从句，其功能和wh-从句的功能相同。例如：　 主语：Whether the plan is feasible remains to be proved.这一计划是否可行还有等证实。　 宾语：Let us know whether / if you can finish the article before Friday.请让我们知道你是否能在星期五以前把文章写完。　 表语：The point is whether we should lend him the money.问题在于我们是否应该借钱给他。　 同位语：They are investigating the question whether the man is trustworthy.　他们调查他是否值得信赖。　 形容词宾语：She\'s doubtful whether we shall be able to come.她怀疑我们是否能够前来。　 介词宾语：I worry about whether he can pass through the crisis of his illness.我担心他是否能度过疾病的危险期。2)选择性疑问从句　 选择性疑问从句由关联词if/whether…or或whethe…or not构成。例如：　Please tell me whether / if they are Swedish or Danish.请告诉我他们是瑞典人还是丹麦人。　I don\'t care whether you like the plan or not.我不在乎你是否喜欢该计划。17.5否定转移1)将think, believe, suppose, expect, fancy, imagine等动词后面宾语从句的否定词转移到主句中，即主句的谓语动词用否定式，而从句的谓语动词用肯定式。例如：　I don\'t think I know you.　我想我并不认识你。　I don\' t believe he will come.　我相信他不回来。注意：若谓语动词为hope,宾语从句中的否定词不能转移。例如：　I hope you weren\'t ill.我想你没有生病吧。2)将seem, appear等后的从句的否定转移到前面。例如：　It doesn\'t seem that they know where to go.看来他们不知道往哪去。　It doesn\'t appear that we\'ll have a sunny day tomorrow.看来我们明天不会碰上好天气。3)有时将动名词，介词短语或整个从句的否定转变为对谓语动词的否定。例如：　I don\'t remember having ever seen such a man.　我记得从未见过这样一个人。(not否定动名词短语having…)　It\'s not a place where anyone would expect to see strange characters on the street.在这里，人们不会想到在街上会碰上陌生的人。(anyone作主语，从句中的谓语动词不能用否定形式。)4)有时状语或状语从句中否定可以转移到谓语动词前。例如：　The ant is not gathering this for itself alone.　(否定状语)　蚂蚁不只是为自己采食。　He was not ready to believe something just because Aristotle said so.(否定because状语)他并不因亚里斯多德说过如何如何，就轻信此事。　She had not been married many weeks when that man\'s younger brother saw her and was struckby her beauty.(否定状语many weeks)　她结婚还不到几个月，这个人的弟弟就看见她了，并对她的美貌着了迷。18.定语从句　定语从句在句中做定语，修饰一个名词或代词，被修饰的名词词组或代词即先行词。定语从句通常出现在先行词之后，由关系词(关系代词或关系副词)引出。关系代词有：who, whom, whose, that, which等。关系副词有：when, where, why等。18.1关系代词引导的定语从句　　关系代词所代替的先行词是人或物的名词或代词，并在句中充当主语、宾语、定语等成分。关系代词在定语从句中作主语时，从句谓语动词的人称和数要和先行词保持一致。1)who, whom, that　 这些词代替的先行词是人的名词或代词，在从句中作主语和宾语。例如：　Is he the man who/that wants to see you?他就是你想见的人吗？(who/that在从句中作主语)　He is the man whom/ that I saw yesterday.他就是我昨天见的那个人。(whom/that在从句中作宾语)2)whose用来指人或物，(只用作定语,若指物，它还可以同of which互换)。例如：　They rushed over to help the man whose car had broken down.　那人车坏了，大家都跑过去帮忙。　Please pass me the book whose(of which)cover is green.　请递给我那本绿皮的书。3)which, that所代替的先行词是事物的名词或代词，在从句中可作主语、宾语等。例如：　　A prosperity which / that had never been seen before appears in the countryside.农村出现了前所未有的繁荣。(which / that在句中作宾语)　　The package(which / that)you are carrying is about to come unwrapped.你拿的包快散了。(which / that在句中作宾语)18.2关系副词引导的定语从句　 关系副词可代替的先行词是时间、地点或理由的名词，在从句中作状语。1)关系副词when, where, why的含义相当于\"介词+ which\"结构，因此常常和\"介词+ which\"结构交替使用。例如：　There are occasions when(on which)one must yield.　任何人都有不得不屈服的时候。　Beijing is the place where(in which)I was born.　北京是我的出生地。　Is this the reason why(for which)he refused our offer?　这就是他拒绝我们帮助他的理由吗？2)that代替关系副词，可以用于表示时间、地点、方式、理由的名词后取代when, where, why和\"介+which\"引导的定语从句，在口语中that常被省略。例如：　His father died the year(that / when / in which)he was born.　他父亲在他出生那年逝世了。　He is unlikely to find the place(that / where / in which)he lived forty years ago.他不大可能找到他四十年前居住过的地方。18.3判断关系代词与关系副词　 方法一： 用关系代词，还是关系副词完全取决于从句中的谓语动词。及物动词后面无宾语，就必须要求用关系代词；而不及物动词则要求用关系副词。例如：　This is the mountain village where I stayed last year.这是我去年呆过的山村。　I\'ll never forget the days when I worked together with you.我永远不会忘记与你共事的日子。　 判断改错：　 (错)This is the mountain village where I visited last year.　 (错)I will never forget the days when I spent in the countryside.　 (对)This is the mountain village(which)I visited last year.　 (对)I\'ll never forget the days(which)I spent in the countryside.　　习惯上总把表地点或时间的名词与关系副词where, when联系在一起。此两题错在关系词的误用上。　 方法二： 准确判断先行词在定语从句中的成分(主、谓、宾、定、状)，也能正确选择出关系代词/关系副词。例1. Is this museum ___ you visited a few days age?　A. where　B. that　C. on which　D. the one例2. Is this the museum ____ the exhibition was held.　A. where　B. that　C. on which　　D. the one答案：例1 D，例2 A例1变为肯定句：This museum is ___ you visited a few days ago.例2变为肯定句：This is the museum ___ the exhibition was held.　　在句1中，所缺部分为宾语，而where, that, on which都不能起到宾语的作用，只有the one既做了主句的表语，又可做从句的宾语，可以省略关系代词，所以应选D。　　而句2中,主、谓、宾俱全，从句部分为句子的状语表地点，既可用副词where，又因in the museum词组，可用介词in + which引导地点状语。而此题中，介词on用的不对，所以选A。　　关系词的选择依据在从句中所做的成分，先行词在从句中做主、定、宾语时，选择关系代词(who, whom, that, which, whose)； 先行词在从句中做状语时，应选择关系副词 (where地点状语，when时间状语，why原因状语) 。18.4限制性和非限制性定语从句1) 定语从句有限制性和非限制性两种。限制性定语从句是先行词不可缺少的部分，去掉它主句意思往往不明确；非限制性定语从句是先行词的附加说明，去掉了也不会影响主句的意思，它与主句之间通常用逗号分开。例如：　　　This is the house which we bought last month.这是我们上个月买的那幢房子。(限制性)The house, which we bought last month, is very nice.这幢房子很漂亮，是我们上个月买的。(非限制性)2) 当先行词是专有名词或物主代词和指示代词所修饰时，其后的定语从句通常是非限制性的。例如：Charles Smith, who was my former teacher, retired last year.查理•史密斯去年退休了，他曾经是我的老师。My house, which I bought last year, has got a lovely garden.　我去年买的的那幢房子带着个漂亮的花园。　　　This novel, which I have read three times, is very touching.这本小说很动人，我已经读了三遍。3) 非限制性定语从句还能将整个主句作为先行词,对其进行修饰,这时从句谓语动词要用第三人称单数。例如：He seems not to have grasped what I meant, which greatly upsets me.他似乎没抓住我的意思，这使我心烦。　　　Liquid water changes to vapor, which is called evaporation.液态水变为蒸汽，这就叫做蒸发。说明：关系代词that和关系副词why不能引导非限制性定语从句。18.5介词+关系词1)介词后面的关系词不能省略。2)that前不能有介词。3)某些在从句中充当时间，地点或原因状语的\"介词+关系词\"结构可以同关系副词when和where互换。例如：　This is the house in which I lived two years ago.这是我两年前住过的房子。　This is the house where I lived two years ago.　Do you remember the day on which you joined our club?还记得你加入我们俱乐部的那一天吗？　Do you remember the day when you joined our club?

18.6 as, which非限定性定语从句　　由as, which引导的非限定性定语从句，as和which可代整个主句，相当于and this或and that。As一般放在句首，which在句中。例如：　　As we know, smoking is harmful to one\'s health.如我们所知，吸烟有害健康。　　The sun heats the earth, which is very important to us.太阳使地球暖起来，这对我们人类很重要。典型例题　1)Alice received an invitation from her boss, ___came as a surprise.

A. it　B. that　C. which　　D. he　 答案C.此为非限定性从句，不能用that修饰，而用which.，it和he都使后句成为句子，两个独立的句子不能单以逗号连接。况且选he句意不通。2)The weather turned out to be very good, ___ was more than we could expect.

A. what　B. which　C. that　D. it　 答案B。which可代替句子，用于非限定性定语从句，而what不可。That不能用于非限定性定语从句，it不为连词，使由逗号连接的两个句子并在一起在英语语法上行不通。3)It rained hard yesterday, ____ prevented me from going to the park..

A. that　B. which　　C. as　D. it　 答案B. as和which在引导非限制性定语从句时，这两个关系代词都指主句所表达的整个意思，且在定语从句中都可以作主语和宾语。但不同之处主要有两点：(1)as引导的定语从句可置于句首，而which不可。(2)as代表前面的整个主句并在从句中作主语时，从句中的谓语必须是系动词；若为行为动词，则从句中的关系代词只能用which.。在本题中，prevent由于是行为动词，所以正确选项应为B。as的用法 例1. the same…as；such…as中的as是一种固定结构,和……一样……。例如：　　I have got into the same trouble as he(has).我碰到了跟他一样的麻烦。例2. as可引导非限制性从句，常带有\'正如\'。例如：　　As we know, smoking is harmful to one\'s health.如我们所知，吸烟有害健康。　　As is known, smoking is harmful to one\'s health.　As是关系代词。例1中的as作know的宾语；例2中，它充当从句的主语，谓语动词know要用被动式。18.7先行词和关系词二合一　1)Whoever spits in public will be punished here.(Whoever可以用anyone who代替)　2)The parents will use what they have to send their son to technical school.(what可以用all that代替)18.8 what/whatever; that/what; who/whoever1)what = the thing which；whatever = anything。例如：　　　What you want has been sent here.你要的动词都送来了。　　　Whatever you want makes no difference to me.不管你要什么，跟我没什么关系。2)who= the person that　whoever= anyone who。例如：　　 (错)Who breaks the law will be punished.　　 (错)Whoever robbed the bank is not clear.　　 (对)Whoever breaks the law will be punished.王子犯法，与庶民同罪。　　 (对)Who robbed the bank is not clear.谁抢了银行还不清楚。3)that和what　　　当that引导定语从句时，通常用作关系代词，而引导名词性从句时，是个不充当任何成分的连接词。宾语从句和表语从句中的that常可省略。What只能引导名词性从句，用作连接代词，作从句的具体成分，且不能省略。例如：　　I think(that)you will like the stamps.我想你会喜欢这些邮票的。　　What we need is more practice.我们需要的是更多的实践。18.9关系代词that的用法1)不用that的情况　　a) 引导非限定性定语从句时。例如：　　　 (错)The tree, that is four hundred years old, is very famous here.　　b) 介词后不能用。例如：　　　　We depend on the land from which we get our food.我们依赖土地获得食物。　　　　We depend on the land that/which we get our food from.

2) 只能用that作为定语从句的关系代词的情况　　a)　在there be句型中，只用that，不用which。　　b)　在不定代词，如：anything, nothing, the one, all, much, few, any, little等作先行词时，只用that，不用which。　　c)　先行词有the only, the very修饰时，只用that。　　　d)　先行词为序数词、数词、形容词最高级时，只用that。.　　e)　先行词既有人，又有物时。例如：　All that is needed is a supply of oil.所需的只是供油问题。　 　Finally, the thief handed everything that he had stolen to the police.那贼最终把偷的全部东西交给了警察。19.状语从句19.1地点状语从句　　地点状语从句通常由where, wherever引导。例如：　　Where I live there are plenty of trees.我住的地方树很多。　　Wherever I am I will be thinking of you.不管我在哪里我都会想到你。19.2方式状语从句　　方式状语从句通常由as,(just)as…so…, as if, as though引导。1)as,(just)as…so…引导的方式状语从句通常位于主句后，但在(just)as…so…结构中位于句首，这时as从句带有比喻的含义，意思是\"正如…\"，\"就像\"，多用于正式文体。例如：　Always do to the others as you would be done by.你希望人家怎样待你，你就要怎样待人。　　As water is to fish, so air is to man.我们离不开空气，犹如鱼儿离不开水。　Just as we sweep our rooms, so we should sweep backward ideas from our minds.　 正如打扫房屋一样，我们也要扫除我们头脑中落后的东西。2)as if, as though　 两者的意义和用法相同，引出的状语从句谓语多用虚拟语气，表示与事实相反，有时也用陈述语气，表示所说情况是事实或实现的可能性较大。汉译常作\"仿佛……似的\"，\"好像……似的\"。例如：　They completely ignore these facts as if(as though)they never existed.他们完全忽略了这些事实，就仿佛它不存在似的。(与事实相反，谓语用虚拟语气。)　　He looks as if(as though)he had been hit by lighting.他那样子就像被雷击了似的。(与事实相反，谓语用虚拟语气。)　It looks as if the weather may pick up very soon.看来天气很快就会好起来。(实现的可能性较大，谓语用陈述语气。)　 说明：as if / as though也可以引导一个分词短语、不定式短语或无动词短语。例如：　He stared at me as if seeing me for first time.他目不转睛地看着我，就像第一次看见我似的。　He cleared his throat as if to say something.他清了清嗓子，像要说什么似的。　The waves dashed on the rocks as if in anger.波涛冲击着岩石，好像很愤怒。19.3原因状语从句比较because, since, as和for：1)because语势最强，用来说明人所不知的原因，回答why提出的问题。当原因是显而易见的或已为人们所知，就用as或since。例如：　I didn\'t go, because I was afraid.我不去是因为我怕。　Since /As the weather is so bad, we have to delay our journey.天气那么糟，旅行推迟了。2)由because引导的从句如果放在句末，且前面有逗号，则可以用for来代替。但如果不是说明直接原因，而是多种情况加以推断，就只能用for。例如：　He is absent today, because / for he is ill.他今天缺席，因为他病了。　He must be ill, for he is absent today.他一定病了，所以今天缺席。19.4目的状语从句　 表示目的状语的从句可以由that, so that, in order that, lest, for fear that, in case等词引导。例如：　You must speak louder so that /in order that you can be heard by all.你必须大点声，别人就能听见了。　He wrote the name down for fear that(lest)he should forget it.他写下了这个名字以免以后忘记。　Better take more clothes in case the weather is cold.最好多穿点衣服，以防天发冷。19.5结果状语从句　结果状语从句常由so…that或such…that引导。so…that与such…that之间可以转换。例如：　　The boy is so young that he can\'t go to school.这男孩年龄太小，不能上学。　He is such a young boy that he can\'t go to school

19.6条件状语从句　连接词主要有if, unless, as/so long as, on condition that等。if引导的条件句有真实条件句和非真实条件句两种。非真实条件句已在虚拟语气中阐述。　unless = if not.　 例如：　Let\'s go out for a walk unless you are too tired.如果不太累，我们去散散步。　If you are not too tied, let\'s go out for a walk.典型例题You will be late ___ you leave immediately.　A. unless　B. until　C. if　　D. or　 答案A。句意：除非你立即走，否则你就回迟到的。可转化为If you dong leave immediately, you will be late。B、D句意不对，or表转折，句子如为You leave immediately or you will be late.

19.7让步状语从句1)though, although引导的让步状语从句，后面的从句不能有but，但是though和yet可连用。例如：Although it\'s raining, they are still working in the field.　虽然在下雨，但他们仍在地里干活。　　He is very old, but he still works very hard.虽然他很老了，但仍然努力地工作。Though the sore be healed, yet a scar may remain.伤口虽愈合，但伤疤留下了。(谚语)2)as, though引导的让步从句必须表语或状语提前(形容词、副词、分词、实义动词提前)。例如：Child as /though he was, he knew what was the right thing to do.虽然是个小孩，该做什么不做什么，他全知道。3)ever if, even though　即使。例如：　　We\'ll make a trip even though the weather is bad.即使天气不好，我们也要去远足。4)whether…or…　不管……都。例如：　　Whether you believe it or not, it is true.信不信由你，这确实是真的。5)　\"no matter +疑问词\"或\"疑问词+后缀ever\"。例如：　　No matter what happened, he would not mind. =Whatever happened, he would not mind.不管发生什么，他不在意。　　　替换：no matter what = whatever　　　　no matter who = whoever　　　　no matter when = whenever　　　　no matter where = wherever　　　　no matter which = whichever　　　　no matter how = however　 注意：no matter不能引导主语从句和宾语从句。　 (错)No matter what you say is of no use now.　 (对)Whatever you say is of no use now.你现在说什么也没用了。(Whatever you say是主语从句)　　(错)Prisoners have to eat no matter what they\'re given,　 (对)Prisoners have to eat whatever they\'re given.囚犯们只能给什么吃什么。19.8比较while, when, as1)as, when引导短暂性动作的动词。例如：　　　Just as / Just when / When I stopped my car, a man came up to me.我一刹车，有一个人向我走来。2)当从句的动作发生于主句动作之前，只能用when引导这个从句，不可用as或while。例如：　　　When you have finished your work, you may have a rest.赶完活后，你可以休息一下。3)从句表示\"随时间推移\"连词能用as，不用when或while。例如：　　　As the day went on, the weather got worse.　日子一天天过去，天气越变越坏。19.9比较until和till　　此两个连词意义相同。肯定形式表示的意思是\"做某事直至某时\"，动词必须是延续性的。否定形式表达的意思是\"直至某时才做某事\"。动词为延续性或非延续性都可以。正确使用这两个连词的关键之一就在于判断句中的动词该用肯定式还是否定式。肯定句：I slept until midnight.我一直睡到半夜时醒了。　　Wait till I call you.等着我叫你。(在肯定句中可用before代替。例如Let\'s get in the wheat before the sun sets.)　 否定句：She didn\'t arrive until 6 o\'clock.她直到6点才到。　Don\'t get off the bus until it has stopped.公共汽车停稳后再下车。I didn\'t manage to do it until you had explained how.直到你教我后，我才会做。区别：1)until可用于句首，而till通常不用于句首。例如：　　Until you told me, I had heard nothing of what happened.直到你告诉我以前，出了什么事我一点也不知道。　　2)until when疑问句中，until要放在句首。例如：　---Until when are you staying?　你呆到什么时候？--- Until next Monday.　呆到下周一。　注意：否定句可用另外两种句式表示。1)Not until…在句首，主句用倒装。例如：　　Not until the early years of the 19th century did man know what heat is.直到19世纪初，人类才知道热为何物。　　 　　Not until I began to work did I realize how much time I had wasted.直到工作，才认识到我已蹉跎了几多岁月。2)It is not until…that… 。例如：It was not until I began to work that I realized how much time I had wasted.

19.10表示\"一…就…\"的结构　hardly/scarcely…when/before, no sooner…than　和as soon as都可以表示\"一…就…\"的意思。例如：　I had hardly / scarcely got home when it began to rain.刚回家，就下起雨来了。　I had no sooner got home than it began to rain.　As soon as I got home, it began to rain.　 注意：如果hardly, scarcely或no sooner置于句首，句子必须用倒装结构。例如：　Hardly / Scarcely had I got home when it began to rain.　No sooner had I got home than it began to rain.

20.连词　　连词不能独立担任句子成分而只起连接词与词，短语与短语以及句与句的作用。连词主要可分为两类：并列连词和从属连词。并列连词用来连接平行的词、词组和分句。如：and, but, or, nor, so, therefore, yet, however, for, hence, as well as, both…and, not only…but also, either…or, neither…nor,(and)then等等。20.1并列连词与并列结构　 并列连词引导两个并列的词、词组或句子。1)　and与or　 判断改错：