高中英语语法易错题型 名词性从句陷阱题(含答案解析)

高中英语语法易错题型 名词性从句陷阱题(含答案解析)
高中英语语法易错题型 名词性从句陷阱题(含答案解析)

最新高中英语语法定语从句总复习

高中英语语法定语从句总复习 郴州资兴三中李俊才 定义:用来说明主句中某一名词或代词(有时也可说明整个主句或主句中一部分)而起定语作用的句子叫 作定语从句。 一、关系带词引导的定语从句 1. 关系代词用来指代先行词是人或物的名词或代词 句子成分用于限制从句或非限制性从句只用于限制性从句 代替人代替物代替人或物主语Who which 主语Whom which that 宾语Whose (=of whom) Whose (=of which) that 例1:This is the detective who came from London. 例2:The book which I am reading is written by Tomas Hardy. 2.关系代词的用法 (1) 如果先行词是all, much, anything, something, nothing, everything, little, none等不定代词,关系代词一般只用that,不用which。例如: All the people that are burst into tears.(所有人都迸出眼泪。) (2) 如果先行词被形容词最高级以及first, last, any, only, few, most, no, some, very等词修饰,关系代词常用that,不用which, who,或whom。 (3) 非限制性定语从句中,不能用关系代词that,作宾语用的关系代词也不能省略。 There are about seven million people taking part in the election, most of whom、are well educated. (4) which还有一种特殊用法,它可以引导从句修饰前面的整个主句,代替主句所表示的整体概念或部分 概念。在这种从句中,which可以作主语,也可以作宾语或表语,多数情况下意思是与and this 相似,并可以指人。例如: He succeeded in the competition, which made his parents very happy. (5) that可指人或物,在从句中作表语,(指人作主语时多用who)仅用于限制性定语从句中。

高考英语陷阱题总结归纳-名词性从句

高考英语陷阱题总结归纳——名词性从句 ◆典型陷阱题分析◆ 1. She was so angry and spoke so fast that none of us understood _______ he said meant. A. that B. what C. that that D. what what 【陷阱】可能误选 B.许多同学一看选项首先就排除了C和D,认为这样两个“引导词”叠 用的情况不太可能。在A和B两个选项中,选项A肯定不行,因为它引导宾语从句时不能 充当句子成分,所以便选择了 B. 【分析】正确答案选 D.第一个what 用作动词meant 的宾语,第二个what 用作动词said 的宾语,即在none of us understood what what he said meant 中,none of us understood 为主 句,what what he said meant 为宾语从句,而在此宾语从句中又包括有what he said 这样一 个主语从句。 2. After _______ had happened he could not continue to work there. A. which B. how C. what D. having 【陷阱】可能误选 A. 【分析】最佳答案选 C.有的同学误选A,是因为认为介词后应接关系代词which,但实 际上,若填关系代词,其前没有先行词,这根据不是一个定语从句。另外,由于had happened 缺主语,所以B和D也不能选。请再做下面一题(答案选B): He pointed to ______ looked like a tomb and said, “Ghost.” A. that B. what C. which D. as 3.“Is ______ you want to say?” asked the teacher. A. this B. that C. all that D. that all 【陷阱】根据中文字面意思误选A或B. 【分析】最佳答案选 D.假若选A或B,那么转换成陈述句即为:This is you want to say. / That is you want to say. 显然句中的两个谓语动词is与want相冲突。选D组成的句子是Is that all you want to say?其中的that 为句子主语,all 为表语,you want to say 为定语从句, 用以修饰all. ?”“When ______ leave for Japan is kept secret.” 4. “When ______ leave for Japan A. they will, will they B. will they, they will C. they will, they will D. will they, will they 【陷阱】可能误选D,认为when 后应用疑问句词序。 【分析】最佳答案选 B.第一个when引出的是一个特殊疑问句,故用疑问词序;第二个 when 引出的是主语从句,故其后用陈述句词序。请做以下试题(答案选C):(1)None knows if _______ that boy, but if _______ him, her parents will be disappointed. A. she will marry, she will marry B. she marries, she marries C. she will marry, she marries D. she marries, she will marry (2)“Where _______ go to work?”“Where _______ go to work is not known.” A. we shall, we shall B. shall we, shall we C. shall we, we shall D. we shall, shall we 5. Someone is ringing the doorbell. Go and see ______.

高中英语语法系列:定语从句

高中英语语法系列:定语从句 知识要点 1.关系代词和关系副词的选用 2.限制性定语从句和非限制性定语从句的区别 3.几组的关系词特殊用法 一、定义:在复合句中,修饰名词或代词的从句叫做定语从句。 The happy man who lives next to me sells vegetables. You must do everything that I do. 被定语从句修饰的词,叫先行词。比如上面两句中的man和everything. 引导定语从句的词,叫关系代词和关系副词。比如who,whom,that,which,wh ere,when,why等 关系词三重作用:①连接主从句;②指代先行词;③在定语从句中担任句子成分。 The man who lives next to me sells vegetables. 该句中,who lives next to me是定语从句,修饰先行词the man,“who”是引导定语从句的关系词,代替先行词the man,在定语从句中作主语。 二、关系词 引导定语从句的关系代词有who,whom,which,that,whose,as等和关系副词w here,when,why等。关系代词和关系副词在定语从句中担任句子成分。

1.用关系代词that,which,who,whom引导的定语从句 who指人,用作主语 whom指人,用作宾语 which指物,用作主语、宾语皆可 that指人和物,用作主语、宾语皆可 The teacher who visits our school today is from Guangzhou. Mrs Read is the person whom you should write to. They planted some trees which didn’t need much water. The fish(which)we bought this morning were not fresh. A plane is a machine that can fly. The noodles(that)I cooked were delicious. 2.用关系代词whose引导的定语从句: 先行词既可指人,也可指物,一般译为“谁的”“什么东西的”,请看例子 The room whose window faces south is mine. 3.用关系副词when、where、why引导的定语从句 (1)when在从句中作时间状语 October lst,1949is the day when(=on which)the People’s Republic of Chin a was founded. (2)where在从句中作地点状语 I recently went to the town where(=in which)I was born. (3)why在从句中作原因状语 The reason why(=for which)he was late was that he missed the train.

名词性从句的解题技巧

名词性从句的解题技巧-标准化文件发布号:(9556-EUATWK-MWUB-WUNN-INNUL-DDQTY-KII

名词性从句解题方法 <方法>——先大类后口诀法 第一步:先分析出大的类别——定从/名从/状从 即分析所缺部分在主句中的成分从而确定从句大的类别第二步:口诀逐一解决: (I)名词性从句。——口诀——先成分后含义 (II)定语从句。——口诀——先成分后先行词 (III)状语从句。——口诀:翻译即可 例如:名词性从句的口诀执行方法是: 分析引导词在从句中的成分 A 做名词性成分——what/which/who/as(+W-ever型) B 做非名词性成分 a 不做成分:that/if/whether(whether霸王原则) b 做状语成分:when/where/why/how 一旦分出AB两类,剩余的靠含义直接翻译即可解决。

例如A computer can only do _________ you have instructed it to do. (01年31题) A. how B. after C. what D. when 解:第一步:先分析出大的类别 A computer can only do中的do是及物动词,后面缺少do的对象,所以考察名词性从句问题 第二步:口诀——先成分后含义 从句you have instructed it to do中的do是及物动词,后面缺少do的对象,所以前面的空在后面的从句内充当名词性成分,所以可以选择的引导词就可以排除AD(因为这两个引导词在从句中是充当状语的),而选项B是名词性从句中不存在的引导词,所以B也不对,最后就剩下一个正确选项C 如此这样一步一步下来,逐一进行排除和选择,最终总是可以直接定位到正确的答案。而这个过程应该是完全被熟化在脑中的一个过程,按部就班的操作直至正确答案自然而然的浮出水面。 其他类别的题目也应该仿照此类,依次完成。 2、建立良好的做题习惯,沉稳面对每一个考验。

高中英语语法大全

(1)表语从句 1.定义:用作表语的从句叫做表语从句。 2.构成:关联词+简单句 3.引导表语从句的关联词的种类: (1) 从属连词that。如: The trouble is that I have lost his address. 麻烦是我把他的地址丢了。 (2) 从属连词whether, as, as if。如: He looked just as he had looked ten years before. 他看起来还与十年前一样。 The question is whether they will be able to help us. 问题是他们是否能帮我们。 注:从属连词if一般不用来引导表语从句,但as if却可引导表语从句,如: All this was over twenty years ago, but it's as if it was only yesterday. gh能跟表语从句的谓语动词一般为系动词be, seem, look等。如: It looked as if it was going to rain. 看起来天要下雨了。 连接副词 where, when, how, why。 如:The problem is who we can get to replace her. 问题是我们能找到谁去替换她呢。 The question is how he did it. 问题是他是如何做此事的。 That was what she did this morning on reaching the attic. 那就是她今晨上了阁楼干的。 解释: 1.连词because可引导表语从句。如: I think it is because you are doing too much. 我想这是因为你做得太多。 2.在一些表示“建议、劝说、命令”的名词后面的表语从句中,谓语动词用虚拟语气。should+动词原形表示,should可省略。如: My suggestion is that we (should) start early tomorrow. 我的建议是我们明天一早就出发。(2)主语从句 1.定义:用作主语的从句叫做主语从句。 2.构成:关联词+简单句 3.引导主语从句的关联词有三类: (1) 从属连词that。如:That they were in truth sisters was clear from the facial resemblance between them. 很明显,她们确是亲姐妹,她们的脸型很相似。 (2) 从属连词whether。如: Whether he’ll come here isn’t clear. 他是否会来这里还不清楚。 (3) 连接代词who, whom, whose, what, which, whoever, whatever, whichever 连接副词 where, when, how, why。如: What she did is not yet known. 她干了什么尚不清楚。 How this happened is not clear to anyone. 这事怎样发生的,谁也不清楚。 Whoever comes is welcome. 不论谁来都欢迎。 Wherever you are is my home ---- my only home. 你所在的任何地方就是我的家----我唯一的家。 解释: 1.主语从句能用it作形式上的主语。常以it作形式主语的句型有: A. It+be+形容词(obvious, true, natural, surprising, good, wonderful, funny, possible, likely, certain, probable, etc.)+that从句。如: It is certain that she will do well in her exam. 毫无疑问她考试成绩会很好。 It is probable that he told her everything. 很可能他把一切都告诉她了。 B. It+be+名词词组(no wonder, an honour, a good thing, a pity, no surprise, etc.)+that

高中英语语法状语从句归纳总结

状语从句一. 二.分类:

adv.+that (如此……以致) so that (结果……) such+n.+that (如果……以致) that (所以,因此) 让步状语从句: though/although 不可同but 连用。 though/although (虽然) however (可是) even though/if (即使) no matter+what/which/where/who/when =whatever/whichever/wherever/whoever/whenever (不论什么/哪一个/哪里/谁/何时) 比较状语从句: as (正如) as…as (和……一样) not as/so … as (不如……) than (比……更) the+比较级…+the+比较级 (越……越……) 条件状语从句: if (假设) unless (如果不) so long as (只要) on condition that (如果) 方式状语从句: as (像……那样地) just as (正像) as if (好像) as though (好像) 三. 四. 各种状语从句的简化方法:

1. 2.以after和before引导的状语从句的主语若与主句主语一致时,从句等于after/before+doing sth. 作状语。 例:After she sang,she left the rich man's house.= After singing,she left the rich man's house.3. 4.以as soon as引导的状语从句的主语若与主句主语一致时,从句等于on+doing sth.,作状语,此时的动词为非延续性动词。 例:Mary began to operate on the wounded soldiers as soon as he arrived at the village. = Mary began to operate on the wounded soldiers on arriving at the village. 5. 6.时间状语从句和条件状语从句的主语和主句主语一致时,有时可简化为不定式作状语。 例:She stopped when she saw her husband.= She stopped to see her husband. If you want to understand the farmers,you must go to the countryside. = To understand the farmers,you must go to the countryside. 7. 8.结果状语从句和目的状语从句的主语与主句主语一致时,可以简化为不定式作状语;若两者主语不一致时,则应简化为不定式的复合结构作状语。 例:He was so tired that he couldn't go any further.= He was too tired to go any further. I came here so that I could ask some questions.= I came here(in order) to ask some questions.9. 10.以when,while引导的时间状语从句和以if引导的条件状语从句的主语若与主句主语一致时,从句等于when/while/if +doing sth.作状语,表示谓语动作发生在该状语动作的进行过程之中。例:When he turned on the radio,he found it broken.= When turning on the radio,he found it broken.While she was walking along the street,she was hit by a car.= While walking along the street,she was hit by a car. 11.原因状语从句的主语与主句主语一致时,可简化为分词短语作状语。 例:Since l didn't know Chinese,I tried to speak to her in English.= Not knowing Chinese,I tried to speak to her in English. 注意:形容词短语也可作表示原因的状语,来代替原因状语从句,放在句首、句末均可,但一般应加逗号。 例:As he was thirsty and eager to get a little rest,he went into the tea-house. = Thirsty and eager to get a little rest,he went into the tea-house. 12.在时间、原因、条件等状语从句中,若从句和主句主语不一致时,可简化为分词复合结构作状语。有时也可简化为“with/without名词或代词十分词(短语)”形式作状语。 例:When the film start appeared, the children got exited.= The film start appearing,the children got exited. If all the work is done, you can have a rest.= With all the work done,you can have a rest. Nothing can live if there is no air.= Nothing can live without air.

高中英语非限定性定语从句语法归纳

非限定性定语从句是英语语法中从句的一种,是定语从句的分支之一。作用是对所修饰的成分作进一步说明,通常和主句间用逗号隔开,将从句拿掉后其他部分仍可成立。运用非限定性定语从句,尤其要注意其语法运用及其所表示的东西。 1 who引导的非限制性定语从句 Our guide,who was a French Canadian,was an excellent cook. 我们的向导,一个法裔加拿大人,擅长于烹调。 My gardener,who is very pessimistic,says that there will be no apples this year. 我家的园丁非常悲观,他说今年将不结苹果。 2 whom引导的非限制性定语从句。 关系代词whom用于指人,在句中作动词宾语和介词宾语,作介词宾语时,介词可位于句末。 如:Peter, whom you met in London, is now back in Paris. 彼得现在回巴黎了,你在伦敦见过他。 Mr Smith,from whom I have learned a lot,is a famous scientist. 史密斯先生是一位著名的科学家,我从他那儿学了许多东西。 3 whose引导的非限制性定语从句。 whose是关系代词who的所有格形式,在从句中作定语。whose通常指人,也可指动物或无生命的事物。 如:The boy, whose father is an engineer, studies very hard. 那位小男孩学习很努力,他的父亲是位工程师。 Above the trees are the mountains, whose magnificence the river faithfully reflects on the surface. 在树林的高处是山,其壮丽的景色完全映照在河面上。 The play,whose style is rigidly formal,is typical of the period. 这剧本是那个时期的典型作品,风格拘谨刻板。 4 which引导的非限制性定语从句。 关系代词which在非限制性定语从句中所指代和修饰的可以是主句中的名词、形容词、短语、其他从句或整个主句,在从句中作主语、动词宾语、介词宾语或表语。 ①which指代主句中的名词,被指代的名词包括表示物、婴儿或动物的名词、表示单数意义的集体名词以及表示职业、品格等的名词。 如:These apple trees,which I planted three years ago,have not borne any fruit. 这些苹果树是我三年前栽的,还没有结过果实。 She is an artist,which I am not. 她是一位艺术家,而我不是。 Water,which is a clear liquid,has many uses. 水是一种清澈的液体,有许多用途。 The two policemen were completely trusted,which in fact they were. 那两个警察完全受到信任,事实上,也真是如此。 ②which指代主句中的形容词。 如:She was very patient towards the children,which her husband seldom was. 她对孩子们很耐心,她丈夫却很少这样。 She is always careless,which we should not be. 她总是马虎大意,我们可不应该这样。 ③which指代主句中的某个从句。

高中英语语法复习之三大从句

三大从句 定语从句 1.The meeting that you have missed yesterday was very important. 2. The girl who is making a speech right now is our monitor. 3. The vase that I broke yesterday was very expensive. 4. The boy who helped you yesterday is my neighbour. 5. That's just the topic that I'm very interested in. 6. He is just the boss who gave me that valuable opportunity. 7. I like the cake which you bought yesterday. 8. He is the teacher who helped me. 9. We all like that speaker who is very humorous. 10. The old lady whose two daughters are both teachers is our neighbour. 11. She is the girl whom I met at the party. 12. There are occasions when one must yield. 13.Beijing is the place where I was born. 14.Is this the reason why he refused our offer? 15. His father died the year when he was born. 16.He is unlikely to find the place in which he lived forty years ago. 17. Do you remember the day on which you joined our club? 18.This is the house in which I lived two years ago. 19. He has finished the difficult exercise, which is easy for you. 20.None of us know the reason for which Tom was absent from the meeting. (why = for which ). 只用that不用which的情况 ①先行词指物且含有不定代词(all, little, few, much, everything, anything等) Do you have anything that you want to say for yourself? All that Lily told me seems untrue. ②先行词被the only, the very, the right, any, every, some, no, just等修饰 This is the very bus that I am waiting for. The only thing that we can do is to lend you some money. ③先行词含有最高级或含有序数词时,如: This train is the last that will go to Suzhou. This is the first two-story bus that runs in our city. What is the most interesting film that you have ever seen? ④先行词既有人又有物

名词性从句练习题(含答案)

名词性从句练习题(含答案) 一、名词性从句 1.______ has caused great confusion is ______ he made it without anyone else's help. A. What; that. B. What; how. C. It; how. D. It; that. 【答案】 B 【解析】【分析】句意:让人极大困惑的是他如何在没有别人帮助的情况下做到这一点的。表示“让人困惑的事情”用what引导主语从句,表示“如何做到的”用how表方式,引导表语从句。故选B. 【点评】考查名词性从句,本题涉及what引导的主语从句和how引导的表语从句。 2. is even more important is the earth cooled down, water began to appear on its surface. A. When; that; when B. What; whether; as C. What; that; as D. lt; whether; as 【答案】 C 【解析】【分析】这题考查从句的用法,第一空填what引导主语从句,在主语从句中what做主语,第二空填that引导表语从句,在表语从句中,as是引导时间状语从句,句意是:甚至更重要的是:随着地球的冷却,水开始出现在表面。选C。 3._______ are playing an important part is well known to us all. A. That who B. Those who C. Who that D. Who 【答案】 D 【解析】【分析】考查主语从句。句意:谁起着重要作用,这是众所周知的。主语从句缺少引导词,从句缺少主语,故选D。 4.Has it been announced ______? A. when are the planes to take off B. that are the planes to take off C. where are the planes to take off D. when the planes are to take off 【答案】 D 【解析】【分析】句意: 飞机什么时候起飞已经宣布了吗?此处是when引导的主语从句,且要用陈述句语序,故选D。 【点评】考查名词性从句,it作形式主语,关系副词when引导的从句作真正的主语。 5.--- made her ashamed of herself? --- the lowest mark in her class. A. What; Because she got B. Was it what; Getting

高中英语语法_状语从句练习30题及详解

1. Tim is in good shape physically he doesn't get much exercise. A. if B. even though C. unless D. as long as 2. The school rules state that no child shall be allowed out of the school during the day, ______ accompanied by an adult. A. once B. when C. if D. unless 3. you may have, you should gather your courage to face the challenge. A. However a serious problem B. What a serious problem C. However serious a problem D. What serious a problem of the heavy traffic,it was already time for lunch break she got to her office. A.since B.that C.when D.until* m John thinks it won’t be long he is ready for his new job. A. when B. after C. before D. since 6. Today, we will begin ________we stopped yesterday so that no point will be left out. A. when B. where C. how D. what 7. She had just finished her homework her mother asked her to practice playing the piano yesterday. A. when B. while C. after D. since 8. My parents don’t mind what job I do I am happy. A. even though B. as soon as C. as long as D. as though 9. You can’t borrow books from the s chool library ______ you get your student card. A. before B. if C. while D. as 10. All the dishes in this menu, otherwise stated, will serve two to three people. A. as B. if C. though D. unless of the financial crisis, days are gone _ _ local 5-star hotels charged 6,000 yuan for

高中英语语法表语从句详解素材

定义 表语从句定义:在一个复合句中,从句作的是主语的表语成分。 A The problem is puzzling. 这个问题令人困惑 主语,连系动词,形容词作表语 The problem is when we can get a pay rise. 问题是什么时候我们可以得到加薪. 主语连系动词一个句子作表语---表语从句 B 连接表语从句的连接词有:that, what, who, when, where, which, why,whether,how.whoever,whomever,whichever ,whatever等 He has become a teacher. 他已经成为一名教师。 He has become what he wanted to be ten years ago. 他已经成为了他10年前想成为的。 She has remained there for an hour. 她曾在那里停留了一个小时。 She has remained where I stood yesterday for an hour. 她一直在我昨天站的地方站了一个小时。 His suggestion is good. 他的建议是好的。 His suggestion is that we should stay calm. 他的建议是,我们应该保持冷静。 The question is confusing. 这个问题令人困惑. The question is when he can arrive at the hotel. 问题是,他什么时候可以到达酒店。 Who will travel with me to Beijing tomorrow.谁与我明天将前往北京。 Why he cried yesterday. 昨天他为什么哭。 How I can persuade her to join us in the party. 我怎么能说服她加入我们的派对。 Whether the enemy is marching towards us. 是否敌人正向我们行进. 注意 A 表语从句一定要用陈述语序。 False: The question is when can he arrive at the hotel. Right: The question is when he can arrive at the hotel. B 不可以用if,而用whether 连接表语从句(as if 例外)。 引导宾语从句时可以互换if/whether 位于介词后要用whether

名词性从句测试题及答案经典

名词性从句测试题及答案经典 一、名词性从句 1.______ has caused great confusion is ______ he made it without anyone else's help. A. What; that. B. What; how. C. It; how. D. It; that. 【答案】 B 【解析】【分析】句意:让人极大困惑的是他如何在没有别人帮助的情况下做到这一点的。表示“让人困惑的事情”用what引导主语从句,表示“如何做到的”用how表方式,引导表语从句。故选B. 【点评】考查名词性从句,本题涉及what引导的主语从句和how引导的表语从句。 2.________ is known to us all that the old scientist, for ________ life was hard in the past, still works hard in his eighties. A. As; whose B. It; whose C. As; whom D. It; whom 【答案】 D 【解析】【分析】句意:我们都知道,那位老科学家,过去生活很艰苦,到了八十多岁还在努力工作。第一空it is known to us all that…是个固定句型,意为“众所周知…”;第二空为介词+关系代词引导的定语从句,先行词the old scientist指人,作介词for的宾语,只能用whom,故选D。 【点评】考查名词性从句和定语从句,本题涉及固定句式it is known to us all that…和whom引导的限制性定语从句。 3.Some people believe _______ has happened before or is happening now will repeat itself in the future. A. whatever B. whenever C. wherever D. no matter what 【答案】 A 【解析】【分析】句意:一些人认为之前发生的或现在正在发生的任何事情在将来都会重复发生。Whatever has happened before or is happening now是一个主语从句,whatever既引导起这个主语从句,也在句中做主语。BC项都属于副词的性质,都不能做主语,通常只能做状语;no matter what只能用来引导状语从句,故选A。 【点评】考查名词性从句,本题涉及"特殊疑问词+ever"引导的主语从句。 4.Has it been announced ______? A. when are the planes to take off B. that are the planes to take off C. where are the planes to take off D. when the planes are to take off 【答案】 D 【解析】【分析】句意: 飞机什么时候起飞已经宣布了吗?此处是when引导的主语从句,且要用陈述句语序,故选D。 【点评】考查名词性从句,it作形式主语,关系副词when引导的从句作真正的主语。

(完整版)高中英语语法专项训练.--状语从句

高中英语语法专项训练----状语从句 1.Don’t be afraid of asking for help _______ it is needed. A. unless B. since C. although D. when 2. A good storyteller must be able to hold his listeners’ curiosity ________ he reaches the end of the story. A. when B. unless C. after D. until 3. _______ I know the money is safe, I shall not worry about it. A. Even though B. Unless C. As long as D. while 4 You will succeed in the end ____ you give up halfway. A. even if B. as though C. as long as D. unless 5.“Was his father very strict with him when he was at school?” “Yes. He had never praised him _______ he became one of the top students in his grade.” A. after B. unless C. until D. when 6. _____ I suggest, he always disagrees. A. However B. Whatever C. Whichever D. Whoever 7. You should put on the notices ______ all the people may see them. A. where B. in which C. at D. for them 8. _____ she goes, there are crowds of people waiting to see her. A. Wherever B. However C. Whichever D. Whoever 9. Mary clapped her hand over her mouth _______ she realized what she had said. A. while B. as soon as C. suddenly D. then 10.________ her faults, she’s Arnold’s mother. Don’t be so rude to her.

相关文档
最新文档