英语语法高手请进
The pen iscomfortable to write with.to write with 作什么句子成分
答：大侠用我随手造的句子作为例句啊
主语+系+形容词+不定式，这个不定式的句子成份，不同的情况有不同的说法。
语法学家还没有统一呢
章振邦在其《新编英语语法》称之为形容词补足成分。
（adjective complementation)又可以分成三种类型第一种类型又有四种情况（有的分五种）,特点：主句的主语是不定式的逻辑主语 1. Henry was happy to hear it. 喜怒哀乐形容词 2. George was lucky to find it. 运气好坏形容词 3. He was anxious to see her. 心理状态、个人态度形容词 4. He is foolish to meet her again. 性格特征、行为表现形容词 (5) He is likely to see Mary. 可能性、确定性形容词 第二种类型 特点： 主句的主语是不定式的逻辑宾语。
1. Mary is easy to teach. --> To teach Mary is easy. 2. The coffee is bitter to taste. X-->不能如上改写。
第三种类型：主句的主语可以是不定式的逻辑主语，也可以是不定式的逻辑宾语：Geroge is quick to take offence.=George takes offence quickly.The clothes are easy to wash.=The clothes was easily.=It is easy to wash the clothes. 本题句属于第二类的第一种。
也有语法说它是状语的。
作什么状语，说不清楚。
高中英语求教
首先你这个程度应该肯定，水平是不错的，你一定要稳步提高，你现在高一，方法或是感觉不对，或是其他原因在高二或高三甚至临近高考会有退步的情况很正常，希望你心态放正然后你不要太急于求成，每天保证一定的题量，阅读量，贵在坚持，每次做题一定要全身心投入，保持考试状态，要求少做质优按照高考要求给你分析如下：完型：错4个不算多也不算少，我高考没错，首先第一遍通读全文，了解大概意思，大概2分钟；第二遍填词，仔细揣摩，每一道都是针对性的考知识点的，最多一道为难你的题，就靠你语感和运气。
1.有的考固定搭配，一定要记牢。
2.有的考介词，连词等，这个也是看你功底，还有前后句子连接。
3.句子结构，语法。
这个一定要分析好句子结构，主谓宾等，结构清晰答题也就容易了。
4.句意区别，不同单词有相似意思，要区分。
5.单词的词性，最多的是形容词，不同的形容词形式用法不同阅读：在高考时这个是要求速度的，首先也是通读一遍，然后是仔细看题，根据题目找答案，一些无关紧要的废话是不要细读的，因为没时间。
每个题都是针对某个细节，或是根据某个地方的推理，在阅读的时候做些记号很多版块都是有方法的，要找到合适你的，先说到这，有不懂的再交流哦
英语问题---英语句型、语法
Amade sb do sth
形容运气不好的成语
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求··五大从句的练习题···
18.1 关系代词引导的定语从句 18.8 what\\\/whatever;that\\\/what; who\\\/whoever 1）what = the thing which；whatever = anything What you want has been sent here. Whatever you want makes no difference to me. 2) who= the person that whoever= anyone who （错）Who breaks the law will be punished. （错）Whoever robbed the bank is not clear. （对）Whoever breaks the law will be punished. （对）Who robbed the bank is not clear.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。
I think (that) you will like the stamps. What we need is more practice.18.9 关系代词that 的用法 1）不用that的情况 a) 在引导非限定性定语从句时。
(错) The tree, that is four hundred years old, is very famous here. b) 介词后不能用。
We depend on the land from which we get our food. 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。
举例： 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。
19.1 地点状语从句 地点状语从句通常由where, wherever 引导。
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。
I didn't go, because I was afraid. Since \\\/As the weather is so bad, we have to delay our journey.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。
He is absent today, because \\\/ for he is ill. He must be ill, for he is absent today.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. He wrote the name down for fear that(lest) he should forget it. Better take more clothes in case the weather is cold.19.5 结果状语从句 结果状语从句常由so… that 或 such…that引导，掌握这两个句型，首先要了解so 和 such与其后的词的搭配规律。
比较：so和 such 其规律由so与such的不同词性决定。
such 是形容词，修饰名词或名词词组，so 是副词，只能修饰形容词或副词。
so 还可与表示数量的形容词many, few, much, little连用，形成固定搭配。
so foolish such a fool so nice a flower such a nice flower so many \\\/ few flowers such nice flowers so much \\\/ little money. such rapid progress so many people such a lot of people （ so many 已成固定搭配，a lot of 虽相当于 many，但 a lot of 为名词性的，只能用such搭配。
） so…that与such…that之间的转换既为 so与such之间的转换。
The boy is so young that he can't go to school. He is such a young boy that he can't go to school19.6 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. Let's go out for a walk unless you are too tired. 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 though, although 注意： 当有though, although时，后面的从句不能有but，但是 though 和yet可连用 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，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）典型例题1） ___she is young, she knows quite a lot. A. When B. However C. Although D. Unless答案：C。
意为虽然她很年轻，却知道许多。
2) as, though 引导的倒装句 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）。
Child as \\\/though he was, he knew what was the right thing to do. = Though he was a small child, he knew what was the right thing to do.注意： a. 句首名词不能带任何冠词。
b. 句首是实义动词，其他助动词放在主语后。
如果实义动词有宾语和状语，随实义动词一起放在主语之前。
Try hard as he will, he never seems able to do the work satisfactorily. = Though he tries hard, he never seems… 虽然他尽了努力，但他的工作总做的不尽人意。
3) ever if, even though. 即使 We'll make a trip even though the weather is bad.4) whether…or- 不管……都 Whether you believe it or not, it is true.5) no matter +疑问词 或疑问词+后缀ever No matter what happened, he would not mind. Whatever happened, he would not mind. 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, as 1）as, when 引导短暂性动作的动词。
Just as \\\/ Just when \\\/ When I stopped my car, a man came up to me.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。
When you have finished your work, you may have a rest.3）从句表示随时间推移连词能用as，不用when 或while。
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 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。
1)Until可用于句首，而till通常不用于句首。
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。
---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。
Not until the early years of the 19th century did man know what heat is. 直到19 世纪初，人类才知道热能是什么。
Not until I began to work did I realize how much time I had wasted. 直到我开始工作，我才认识到了我已蹉跎了几多岁月。
(2) It is not until… that… 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： I had hardly \\\/ scarcely got home when it began to rain. 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： Hardly \\\/ Scarcely had I got home when it began to rain. No sooner had I got home than it began to rain.17. 名词性从句 在句子中起名词作用的句子叫名词从句 (Noun Clauses）。
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。
17.2 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，这一事实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. 俱乐部将给得胜者设奖。
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。
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。
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。
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。
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。
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 struck by 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。
形容今日反思的句子有哪些
分类 导名词性从句的连接词可分为三 连词（5个that （宾语从句或表语从句that有时可以省略） whether,if （均表示“是否”表明从句内容的不确定性） as if ,as though （均表示“好像”，“似乎”） 以上在从句中均不充当任何成分 连接代词（9个）：what, whatever, who, whoever, whom, whomever, whose, which, whichever 连接副词（7个）：when, where, how, why, whenever, wherever, however 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。
That she was chosen made us very happy. We heard the news that our team had won.比较 whether与if 均为是否的意思。
但在下列情况下，只可用whether： 1. whether引导主语从句并在句首 eg:whether he can come to the party on time depends on the traffic 2. 引导表语从句 eg:The question is whether we can get in touch with her 3. whether从句作介词宾语 eg:I am thinking about whether I should quit my present job 4.if与whether都可以与or not 连用，但后面紧跟or not 时只能用whether we didn't know whether or not she was ready.（此时只能用whether） I wonder whether\\\/if the news is true or not.（此时则二者都可以用） 5. 引导同位语从句 Whether he will come is not clear. 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。
It is not important who will go. It is still unknown which team will win the match. 作句子主语的从句叫主语从句。
主语从句通常由下列词引导： 1）从属连词that，whether 等； 2）连接代词what，who，which，whatever，whoever，whom 等； 3) 连接副词how，when，where，why 等。
that在句中无词义，只起连接作用；连接代词和连接副词在句中既保留自己的疑问含义、又起连接作用，在从句中充当从句的成分。
注：whom、who指人，what指物，whatever，whoever表示泛指意义。
例如： What he wants to tell us is not clear. 他要跟我们说什么，还不清楚。
Who will win the match is still unknown. 谁能赢得这场比赛还不得而知。
It is known to us how he became a writer. 我们都知道他是如何成为一名作家的。
Where the English evening will be held has not yet been announced. 英语晚会将在哪里举行，还没有宣布。
有时为避免句子头重脚轻，常用形式主语it代替主语从句作形式主语放于句首，而把主语从句置于句末。
主语从句后的谓语动词一般用单数形式。
常用句型如下： （1）It is+ 名词 + that从句 （2）It is + 形容词 + that从句 （3）It is + 动词的过去分词+ 主语从句 （4）It + 不及物动词 + that 从句 另注意在主语从句中用来表示惊奇、不相信、惋惜、理应如此等语气时，谓语动词要用虚拟语气“(should) +do”，常用的句型有： It is necessary (important, natural, strange, etc.) that … It is suggested (requested, proposed, desired, etc.) that… 名词从句用作宾语的从句叫宾语从句。
引导宾语从句的关联词与引导主语从句表语从句的关联词大致一样，在句中可以作谓语动词或介词及非谓语动词的宾语。
1. 由连接词that引导的宾语从句 由连接词that引导宾语从句时，that在句中不担任任何成分，在口语或非正式的文体中常被省去，但如从句是并列句时,第二个分句前的that不可省。
例如： He has told me that he will go to Shanghai tomorrow. 他已经告诉我他明天要去上海。
We must never think (that) we are good in everything while others are good in nothing. 我们决不能认为自己什么都好，别人什么都不好。
注意：在demand、order、suggest、decide、insist, desire, request, command, doubt等表示要求、命令、建议、决定等意义的动词后，宾语从句常用“（should）+ 动词原形”。
例如： I insist that she (should) do her work alone. 我坚持要她自己工作。
The commander ordered that troops (should) set off at once. 司令员命令部队马上出发。
2. 用who，whom, which, whose, what, when, where, why, how, whoever, whatever, whichever等关联词引导的宾语从句相当于特殊疑问句，应注意句子语序要用陈述语序。
例如： I want to know what he has told you. 我想知道他告诉了你什么。
She always thinks of how she can work well. 她总是在想怎样能把工作做好。
She will give whoever needs help a warm support. 凡需要帮助的人，她都会给予热情的支持。
3. 用whether或if引导的宾语从句，其主语和谓语的顺序也不能颠倒，仍保持陈述句语序。
此外，whether与if 在作“是否”的意思讲时在下列情况下一般只能用whether，不用if： a. 引导主语从句并在句首时；b. 引导表语从句时；c . 引导从句作介词宾语时；d. 从句后有“or not”时；e. 后接动词不定式时。
例如： Whether there is life on the moon is an interesting question. 月球上有没有生命是个有趣的问题。
Everything depends on whether we have enough money. 一切要看我们是否有足够的钱。
I wonder whether he will come or not. 我想知道他来还是不来。
Can you tell me whether to go or to stay? 你能否告诉我是去还是留
4. 注意宾语从句中的时态呼应，当主句动词是现在时，从句根据自身的句子情况，而使用 不同时态。
例如： I know (that) he studies English every day. （从句用一般现在时） I know (that) he studied English last term. （从句用一般过去时） I know (that) he will study English next year. （从句用一般将来时） I know (that) he has studied English since 1998. （从句用现在完成时） 当主句动词是过去时态（could, would除外），从句则要用相应的过去时态，如一般过去时，过去进行时，过去将来时等；当从句表示的是客观真理，科学原理，自然现象，则从句仍用现在时态。
例如： The teacher told us that Tom had left us for America． 5. think, believe, imagine, suppose等等动词引起的否定性宾语从句中，要把上述主句中的动词变为否定式。
即将从句中的否定形式移到主句中。
例如： We don’t think you are here. 我们认为你不在这。
I don’t believe he will do so. 我相信他不会这样做。
在复合句中，位于系动词之后作表语的从句叫表语从句。
引导表语从句的关联词与引导主语从句的关联词大致一样，表语从句位于连系动词后，有时用as if引导。
其基本结构为：主语 + 系动词 + that从句。
例如： The fact is that we have lost the game. 事实是我们已经输了这场比赛。
That’s just what I want. 这正是我想要的。
This is where our problem lies. 这就是我们的问题所在。
That is why he didn’t come to the meeting. 那就是他为什么不到会的原因。
It looks as if it is going to rain. 看上去天要下雨了。
需要注意的，当主语是reason时，表语从句要用that引导而不是because。
例如： The reason why he was late was that he missed the train by one minute this morning . 【注意】whether 可引导表语从句，但与之同义的if却通常不用于引导表语从句。
编辑本段五、同位语从句 同位语从句说明其前面的名词的具体内容。
同位语从句通常由that引导，可用于同位语从句的名词有advice、demand、doubt、fact、hope、idea、information、message、news、order、problem、promise、question、request、suggestion、truth、wish、word等。
例如： The news that we won the game is exciting. 我们赢得这场比赛的消息令人激动。
I have no idea when he will come back home. 我不知道他什么时候回来。
The thought came to him that Mary had probably fallen ill. 他想到可能玛丽生病了。
同位语从句和定语从句的区别： that作为关系代词，可以引导定语从句，充当句子成分，在从句中作宾语时可以省略； that引导同位语从句时，起连词的作用，没有实际意义，不充当句子成分，一般不能省略。
试比较下面两个例句: I had no idea that you were here．（that引导同位语从句，不能省略） Have you got the idea（that）this book gives you of life in ancient Greece
（that引导定语从句，作宾语，可以省略） （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 she is still alive is her luck. 她还活着全靠运气。
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，这一事实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… 众所周知…… 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-从句 It appears that… 似乎…… It happens that… 碰巧…… It occurred to me that… 我突然想起…… 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. 俱乐部将给得胜者设奖。
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。
编辑本段八、if, whether引导的名词从句 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待证实。
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。
选择性疑问从句由关联词if\\\/whether…or或whether…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。
if和whether的区别： 1、 在动词不定式之前只能用whether 。
如： 例8 I can’t decide whether to stay. 我不能决定是否留下。
2、 在whether …… or not 的固定搭配中。
如： 例9 I want to know whether it’s good news or not . 我想知道是否是好消息。
3 、在介词后，只能用whether。
如： 例10 His father is worried about whether he lose his work . 他的父亲担心是否会失去工作。
4、宾语从句放在句首表示强调时，只能用whether 。
如： Whether this is true or not, I really don’t know. 这是否真的，我真的不知道。
（例11 Whether they can finish the work on time is still a problem . 他们是否能准时完成这项工作还是个问题。
－－此例为主语从句，有误，感谢指出） 5、用if会引起歧义时，只用whether。
如： 例12 Could you tell me if you know the answer ? 这句话有两种意思：“你能告诉我是否知道答案吗
”或“如果你知道答案，请告诉我，好吗
”。
如用whether可避免歧义.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。
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。
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。
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。
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。
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 struck by her beauty. (否定状语many weeks) 她结婚还不到几个星期，这个人的弟弟就看见她了，并对她的美貌着了迷。
