引导主语从句的连词主要有：
从属连词：that whether
连接代词：who whoever whom whose what whatever which whichever
连接副词：when where how why whenever wherever however
1、常规主语从句，即句子在复合句中充当一个主语。主语从句的时态不受主句时态的影响和限制。
例句
（1）Who will be our monitor hasn't been decided yet.
现在还没有决定谁会成为我们的班长。
（2）Whatever you did is right.
你做的任何事都是正确的。
（3）What we need is time.
我们需要的是时间。
2、名词性从句的时态规则：
主句谓语动词是现在或将来时，从句谓语动词可以用任何需要的时态。
I wonder what he is doing now.我想知道他现在在干什么。
Do you know when and where he was born?你知道他在何时何地出身吗？
主句谓语动词是过去时，从句谓语动词一般需用过去时。
（1）从句与主句的谓语动作同时发生，从句用一般过去时或过去进行时。
I thought that he studied hard.我认为他学习很努力。
He told me his son was watching TV.他告诉我他的儿子在看电视。
（2）从句谓语动作在主句谓语动作之后，从句用过去将来时。
He said he would spend his holidays in Qingdao.他告诉我他将在青岛度假。
（3）从句谓语动作在主句谓语动作之前，从句用过去完成时。
They told me they had waited for me half an hour.他们告诉我他们已经等了我半小时了。
（4）从句如果有表示过去某一具体时间的状语，仍用过去时。
She told me her brother died in 1945.她告诉我她的哥哥（弟弟）死于1945年。
从句时态不受下列客观的条件影响。
（1）从句说明的是不受时间限制的事实或真理（客观真理）。
The teacher told us that the earth turns from west to east.老师告诉我们地球自西向东转。
He said Asia is the largest continent.他说亚洲是最大的大陆。
（2）当从句表示的是反复出现的时态不变。
She told me that she gets up at six o'clock every morning.她告诉我她每天早晨6点起床。
He asked me when the train usually starts.他向我询问火车通常何时出发。
（3）当从句的谓语动作仍在继续时，或者表示现在仍在的状态时，时态不变。
She told me the other day that she is only 10.她告诉我那天她只有10岁。
（4）当从句的动作状态还未发生，要用一般式表示。强调与现在的联系。
He said he will wait for me this evening.他说他今晚将等待我。
3、为了防止句子头重脚轻，通常把形式主语it放在句首位置，真正主语搁置于句末
It is certain that he will win the match.他一定会赢得这场比赛的。
It is very likely that they will hold a meeting.他们很有可能会举行一场会议。
扩展资料
用it 作形式主语的结构
(1) It is +名词+that从句
It is a fact that … 事实是……
It is an honor that …非常荣幸
It is common knowledge that …是常识
(2) it is +形容词+that从句
It is natural that… 很自然……
It is strange that… 奇怪的是……
(3) it +不及物动词+that从句
It seems that… 似乎……
It happened that… 碰巧……
(4) it is+过去分词+that从句
It is reported that… 据报道……
It has been proved that… 已证实……
参考资料来源：百度百科-主语从句
温馨提示：答案为网友推荐，仅供参考
第1个回答 推荐于2017-11-25
主语从句
一、概述：在句子中起名词作用的各种从句统称为名词性从句。根据它们在句中的语法作用，这类从句又可分为主语从句、同位语从句、表语从句和宾语从句。
二、 几个共性问题：
1．连接方式
（1） 在由连词that, whether, if引导的名词性从句中，引导词在句中不做成分，在宾语从句和表语从句中，that可以省略。
（2） 在由连接代词who, whose, whom, which, what, whoever, whomever, whichever, whatever引导的名词性从句中，其连接代词在句中起名词性作用，担当一定成分。
（3）在由连接副词when, where, why, how引导的名词性从句中，其连接副词在句中作状语。
2．whether和if的区别
（1）whether在引导的主语从句中可以置于句首，而if则不能。
（2）whether可以与or not连用，or not可以紧跟在whether之后，也可以置于从句末尾；if一般不能和or not连用。
（3）表语从句、同位语从句和介词宾语从句（即在系词be和介词之后），只能用whether连接，而不用if。
（4）从句是否定式时，一般用if, whether很少用在否定式从句中。
例如：I don’t care if he doesn’t come . 如果他不来，我也不介意。
The problem is whether we can carry out the plan.
问题是我们是否能实施这项计划。
三、 主语从句
1．主语从句主要有三类：
（1） 由连词that引导的主语从句。
例如：That you will win the medal seems unlikely.
你想获得奖牌看起来是不可能的。
That you are so indifferent bothers me.
你如此冷淡使我很烦恼。
That she survived the accident is a miracle.
她在事故中幸免于难简直是奇迹。
（2） 用连接代词或连接副词if, whether 引导的主语从句。
例如： Which of them escaped from the prison is still a mystery.
他们哪一个是从监狱里逃跑的，仍然是个谜。
When they will come hasn’t been made pubic.
他们什么时候来还不知道。
Whether she is coming or not doesn’t matter too much.
她来不来都无关紧要。
（3） 用关系代词引导的主语从句。
例如：What you need is more practice.
你所需要的是更多的训练。
What I want to know is this. 我想知道的就是这事。
Whatever we do is to serve the people.
我们无论做什么都是为人民服务。
主语从句可以直接放在主语位置上，也可以用it作形式主语，
而将从句放在句末（尤其是当谓语较短时）。
例如：That light travels in straight lines is known to all.
光沿直线传播，这是众所周知的事。
=It is known to all that light travels in straight lines.
众所周知光沿直线传播。
When the plane is to take off has not been announced .
飞机何时起飞还没有宣布。
= It has not been announced when the plane is to take off.
还没有宣布飞机何时起飞。
当what引导的主语从句表示“…的东西”时，一般不用it作形式主语。
错:It is a book what he wants.
对:What he wants is a book. 他想要的是本书。
如果带主语从句的句子是疑问式，则必须用it作形式主语的结构。
例如：Has it been settled who will be sent to carry out the task ?
谁将被派去执行这项任务决定了吗 ？
3．固定用法和译法
（1） It is +名词+从句
It is a fact that… 事实是……
It is good news that … ……是好消息
It is a question that … ……是个问题
It is common knowledge that … ……是常识
类似的名词还有：a pity；a wonder；a good thing； no wonder； surprise等。
例如：It is a mystery to me how it all happened.
这一切是怎么发生的是个谜。
It is common knowledge that the whale is not a fish.
鲸鱼不是鱼，这是常识。
It is no surprise that Bob should have won the game.
鲍勃会赢得这场比赛，这不足为奇。
（2） It is +形容词+从句
It is necessary that … 有必要……
It is clear that … 很清楚……
It is likely that … 很可能……
It is important that … 重要的是……
类似的形容词还有：strange; natural; obvious; true; good; wonderful; possible; unlikely; quite; unusual; certain; evident; worth-while; surprising; interesting; astonishing, etc.
例如：It is obvious that conductors and insulators are both important in industry.
很明显导体和绝缘体在工业中都很重要。
It is doubtful whether she will be able to come.
她是否能来令人怀疑。
It was really astonishing that he refused to talk to you .
他拒绝和你说话真是令人惊讶。
It is essential that he should be here by the weekend .
周末之前，他应该到这里是必要的。
It seems obvious that we can not go on like this.
很明显我们不能这样下去了。
（3） It is +过去分词+从句
It is said that … 据说……
It is reported that … 据报道……
It has been proved that … 已证明……
It must be proved that… 必须指出……
类似的过去分词还有：known; estimated; expected; believed; thought; hoped; noted; discussed; required; decided; suggested; demanded; made clear; found out,etc.
例如：It is thought that he is the best player.
大家都认为他是最好的选手。
It is estimated that the vase is 2000 years old.
据估计这个花瓶有2000年的历史。
It is used to be thought that a new star must be due to a collision between two stars. 过去一直认为新星是由于两颗星星之间碰撞产生的。
It has not been made clear when the new road is to be opened to traffic.
还没弄清楚这条路将开始通车。
（4） It +不及物动词+从句
It seems that … 好像是……
It happened that… 碰巧……
It follows that … 由此可见……
It has turned out that … 结果是……
类似的不及物动词还有：seem, appear, occur, follow, happen, turn out, etc.
例如：It turned out that nobody remembered the address.
结果是无人记得那个地址。
It now appears that they are in urgent need of help.
看起来他们急需帮助。
It does not matter if I missed my train, because there is another later.
没有赶上这趟火车没有关系，稍晚还有一趟。
It happened that I saw him yesterday.
碰巧我昨天看见他了。
当“及物动词 + 宾语”较短时，也可用这种结构。
例如：It shocked me that Peter did not tell anybody where he was.
让我吃惊的是彼得没有告诉任何人他在哪里。
It does not interest me whether you go or not.
我对你去不去不感兴趣。
It +某些固定结构+ 主语从句。
例如：It doesn’t make too much difference （It doesn’t make any difference / It doesn’t alter the situation），whether it rains or not . 下不下雨都没有多大关系。
It does not make any difference whether it rains or not .
下不下雨没什么分别。
It does not make the least difference to me what you do.
对我来说你做什么都无关紧要。
Is it of much consequence to you that Mr. Wang has failed to do it ? 王先生没有做成这件事对你有什么重要影响吗？追问
一、概述：在句子中起名词作用的各种从句统称为名词性从句。根据它们在句中的语法作用，这类从句又可分为主语从句、同位语从句、表语从句和宾语从句。
二、 几个共性问题：
1．连接方式
（1） 在由连词that, whether, if引导的名词性从句中，引导词在句中不做成分，在宾语从句和表语从句中，that可以省略。
（2） 在由连接代词who, whose, whom, which, what, whoever, whomever, whichever, whatever引导的名词性从句中，其连接代词在句中起名词性作用，担当一定成分。
（3）在由连接副词when, where, why, how引导的名词性从句中，其连接副词在句中作状语。
2．whether和if的区别
（1）whether在引导的主语从句中可以置于句首，而if则不能。
（2）whether可以与or not连用，or not可以紧跟在whether之后，也可以置于从句末尾；if一般不能和or not连用。
（3）表语从句、同位语从句和介词宾语从句（即在系词be和介词之后），只能用whether连接，而不用if。
（4）从句是否定式时，一般用if, whether很少用在否定式从句中。
例如：I don’t care if he doesn’t come . 如果他不来，我也不介意。
The problem is whether we can carry out the plan.
问题是我们是否能实施这项计划。
三、 主语从句
1．主语从句主要有三类：
（1） 由连词that引导的主语从句。
例如：That you will win the medal seems unlikely.
你想获得奖牌看起来是不可能的。
That you are so indifferent bothers me.
你如此冷淡使我很烦恼。
That she survived the accident is a miracle.
她在事故中幸免于难简直是奇迹。
（2） 用连接代词或连接副词if, whether 引导的主语从句。
例如： Which of them escaped from the prison is still a mystery.
他们哪一个是从监狱里逃跑的，仍然是个谜。
When they will come hasn’t been made pubic.
他们什么时候来还不知道。
Whether she is coming or not doesn’t matter too much.
她来不来都无关紧要。
（3） 用关系代词引导的主语从句。
例如：What you need is more practice.
你所需要的是更多的训练。
What I want to know is this. 我想知道的就是这事。
Whatever we do is to serve the people.
我们无论做什么都是为人民服务。
主语从句可以直接放在主语位置上，也可以用it作形式主语，
而将从句放在句末（尤其是当谓语较短时）。
例如：That light travels in straight lines is known to all.
光沿直线传播，这是众所周知的事。
=It is known to all that light travels in straight lines.
众所周知光沿直线传播。
When the plane is to take off has not been announced .
飞机何时起飞还没有宣布。
= It has not been announced when the plane is to take off.
还没有宣布飞机何时起飞。
当what引导的主语从句表示“…的东西”时，一般不用it作形式主语。
错:It is a book what he wants.
对:What he wants is a book. 他想要的是本书。
如果带主语从句的句子是疑问式，则必须用it作形式主语的结构。
例如：Has it been settled who will be sent to carry out the task ?
谁将被派去执行这项任务决定了吗 ？
3．固定用法和译法
（1） It is +名词+从句
It is a fact that… 事实是……
It is good news that … ……是好消息
It is a question that … ……是个问题
It is common knowledge that … ……是常识
类似的名词还有：a pity；a wonder；a good thing； no wonder； surprise等。
例如：It is a mystery to me how it all happened.
这一切是怎么发生的是个谜。
It is common knowledge that the whale is not a fish.
鲸鱼不是鱼，这是常识。
It is no surprise that Bob should have won the game.
鲍勃会赢得这场比赛，这不足为奇。
（2） It is +形容词+从句
It is necessary that … 有必要……
It is clear that … 很清楚……
It is likely that … 很可能……
It is important that … 重要的是……
类似的形容词还有：strange; natural; obvious; true; good; wonderful; possible; unlikely; quite; unusual; certain; evident; worth-while; surprising; interesting; astonishing, etc.
例如：It is obvious that conductors and insulators are both important in industry.
很明显导体和绝缘体在工业中都很重要。
It is doubtful whether she will be able to come.
她是否能来令人怀疑。
It was really astonishing that he refused to talk to you .
他拒绝和你说话真是令人惊讶。
It is essential that he should be here by the weekend .
周末之前，他应该到这里是必要的。
It seems obvious that we can not go on like this.
很明显我们不能这样下去了。
（3） It is +过去分词+从句
It is said that … 据说……
It is reported that … 据报道……
It has been proved that … 已证明……
It must be proved that… 必须指出……
类似的过去分词还有：known; estimated; expected; believed; thought; hoped; noted; discussed; required; decided; suggested; demanded; made clear; found out,etc.
例如：It is thought that he is the best player.
大家都认为他是最好的选手。
It is estimated that the vase is 2000 years old.
据估计这个花瓶有2000年的历史。
It is used to be thought that a new star must be due to a collision between two stars. 过去一直认为新星是由于两颗星星之间碰撞产生的。
It has not been made clear when the new road is to be opened to traffic.
还没弄清楚这条路将开始通车。
（4） It +不及物动词+从句
It seems that … 好像是……
It happened that… 碰巧……
It follows that … 由此可见……
It has turned out that … 结果是……
类似的不及物动词还有：seem, appear, occur, follow, happen, turn out, etc.
例如：It turned out that nobody remembered the address.
结果是无人记得那个地址。
It now appears that they are in urgent need of help.
看起来他们急需帮助。
It does not matter if I missed my train, because there is another later.
没有赶上这趟火车没有关系，稍晚还有一趟。
It happened that I saw him yesterday.
碰巧我昨天看见他了。
当“及物动词 + 宾语”较短时，也可用这种结构。
例如：It shocked me that Peter did not tell anybody where he was.
让我吃惊的是彼得没有告诉任何人他在哪里。
It does not interest me whether you go or not.
我对你去不去不感兴趣。
It +某些固定结构+ 主语从句。
例如：It doesn’t make too much difference （It doesn’t make any difference / It doesn’t alter the situation），whether it rains or not . 下不下雨都没有多大关系。
It does not make any difference whether it rains or not .
下不下雨没什么分别。
It does not make the least difference to me what you do.
对我来说你做什么都无关紧要。
Is it of much consequence to you that Mr. Wang has failed to do it ? 王先生没有做成这件事对你有什么重要影响吗？追问
虽然我看见过。
本回答被提问者采纳第2个回答 2013-07-30
主语从句(Subject Clause)
定义:在复合句中充当主语的句子叫做主语从句.
第一部分：常规主语从句，即句子在复合句中充当一个主语
主语从句的时态：不受主句的时态影响和限制。
（1）That he finished writing the composition in such a short time surprised us all.
（2）Whether we will go for an outing tomorrow remains unknown.
（3）Who will be our monitor hasn't been decided yet.
（4） Whom we must study for is a question of great importance.
（5）What caused the accident remains unknown.
（6）Whatever you did is right.
（7）Whose watch was lost is unknown.
（8）What we need is time.
（9）What we need are good doctors.
小结:
（1)引导主语从句连词有that,whether,who,what,whatever等
（2)连词位于句首不能省略
（3)主语从句大多数情况下视为三单,但也有例外,如例9
第二部分：为了防止句子头重脚轻，通常把形式主语it放在主语位置，真正主语搁置于句末
（1）It is certain that he will win the match.
（2）It is true that he has made a very important discovery in chemistry.
（3）It is very likely that they will hold a meeting.
（4）It is strange that he should do that.
（5）It is important that we all should attend the meeting.
（6）It is strange that the man should have stuck to his silly ideas.
（7）It is a pity that we won't be able to go to the south to spend our summer vacation.
（8）It is still a mystery what caused the accident.
（9）It is said that he has gone to shanghai.(=He is said to have gone to shanghai)
（10）It is known to all that the gun powder was first invented by the Chinese.
（11）It is suggested that the work should be done with great care.
（12）It seems that he has seen the film.(=He seems to have seen the film)
（13）It happened that the two cheats were there. (=The two cheats happened to be there)
小结:
（1)以that 引出的主语从句,常以形式主语it引导. It is +形容词/名词/某些动词ed + that 从句.
（2) 在有些that从句中要用虚拟语气 (should+do/should+have done)例句4,5,6,11.
主语从句与宾语从句两者的用法和在句中的作用是不同的，下面从它们的各自用法，介绍：）~
一．主语从句
主语从句 定义:在句子中担当主语的是一个从句,这个从句就叫做主语从句。
主语从句是在复合句中充当主语的从句，通常放在主句谓语动词之前或由形式主语it代替，而本身放在句子末尾。
1. It 作形式主语和it引导强调句的比较
It 作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。而it引导的强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词that。被强调部分指人是也可用who/whom。例如：
It is a pity that you didn’t go to see the film.
2. 用it 作形式主语的结构
(1) It is ＋名词＋从句
It is a fact that … 事实是…
It is an honor that …非常荣幸
It is common knowledge that …是常识
(2) it is ＋形容词＋从句
It is natural that… 很自然…
It is strange that… 奇怪的是…
(3) it ＋不及物动词＋从句
It seems that… 似乎…
It happened that… 碰巧…
(4) it is＋过去分词＋从句
It is reported that… 据报道…
It has been proved that… 已证实…
3. 主语从句不可位于句首的五种情况
(1) if 引导的主语从句不可居于复合句句首。
(2) It is said , (reported) …结构中的主语从句不可提前。例如：
It is said that President Jingo will visit our school next week.
(3) It happens…, It occurs… 结构中的主语从句不可提前。例如：
It occurred to him that he failed in the examination.
(4) It doesn’t matter how/whether …结构中的主语从句不可提前。例如：
It doesn’t matter whether he is wrong or not.
(5) 含主语从句的复合句是疑问句时，主语从句不可提前。例如：
Is it likely that it will rain in the evening?
4. What 与that 在引导主语从句时的区别
What 引导主语从句时在从句中充当句子成分，如主语．宾语．表语，而that 则不然。例如：
What you said yesterday is right.
二：宾语从句的几个特征：1、引导词：what\which\whose\when\whether\if\where
2语序：宾语从句必须是用陈述语句。
如：I think that you must work harder.
宾语从句的引导词、连接词的区别、否定转移等现象。
(1)表达时间的几个句型：一般用when或者是what time：
What time will the train leave?
由于时刻都是固定的，也可以用一般现在时代替一般将来时：
What time does the train leave?
(2)时间的表达方式：8：19(nineteen past eight),7:57(three to eight)，在时间的中间也可以加上分的单词(minutes)
(3)had better +动词原型。意思是提要求，建议。但是上下级不能用这种方式，因为语气太重：
You had better give up smoking .
(4)sb leave sth +地点
I left my book in my classroom yesterday.
(5)may I have your name(address\age)?一般询问对方的年龄、名字等，不要习惯以前的问法，这样很不礼貌，而是要采访上面的问法。以前的习惯是：how old are you? \what's your name?
(6)修饰名词的代词次序：限-描-大-形---年---颜----籍----物--------类+名词：
this is a bridge.
This is a beautiful bridge
补充：从句的语序永远是陈述句。
定义:在复合句中充当主语的句子叫做主语从句.
第一部分：常规主语从句，即句子在复合句中充当一个主语
主语从句的时态：不受主句的时态影响和限制。
（1）That he finished writing the composition in such a short time surprised us all.
（2）Whether we will go for an outing tomorrow remains unknown.
（3）Who will be our monitor hasn't been decided yet.
（4） Whom we must study for is a question of great importance.
（5）What caused the accident remains unknown.
（6）Whatever you did is right.
（7）Whose watch was lost is unknown.
（8）What we need is time.
（9）What we need are good doctors.
小结:
（1)引导主语从句连词有that,whether,who,what,whatever等
（2)连词位于句首不能省略
（3)主语从句大多数情况下视为三单,但也有例外,如例9
第二部分：为了防止句子头重脚轻，通常把形式主语it放在主语位置，真正主语搁置于句末
（1）It is certain that he will win the match.
（2）It is true that he has made a very important discovery in chemistry.
（3）It is very likely that they will hold a meeting.
（4）It is strange that he should do that.
（5）It is important that we all should attend the meeting.
（6）It is strange that the man should have stuck to his silly ideas.
（7）It is a pity that we won't be able to go to the south to spend our summer vacation.
（8）It is still a mystery what caused the accident.
（9）It is said that he has gone to shanghai.(=He is said to have gone to shanghai)
（10）It is known to all that the gun powder was first invented by the Chinese.
（11）It is suggested that the work should be done with great care.
（12）It seems that he has seen the film.(=He seems to have seen the film)
（13）It happened that the two cheats were there. (=The two cheats happened to be there)
小结:
（1)以that 引出的主语从句,常以形式主语it引导. It is +形容词/名词/某些动词ed + that 从句.
（2) 在有些that从句中要用虚拟语气 (should+do/should+have done)例句4,5,6,11.
主语从句与宾语从句两者的用法和在句中的作用是不同的，下面从它们的各自用法，介绍：）~
一．主语从句
主语从句 定义:在句子中担当主语的是一个从句,这个从句就叫做主语从句。
主语从句是在复合句中充当主语的从句，通常放在主句谓语动词之前或由形式主语it代替，而本身放在句子末尾。
1. It 作形式主语和it引导强调句的比较
It 作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。而it引导的强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词that。被强调部分指人是也可用who/whom。例如：
It is a pity that you didn’t go to see the film.
2. 用it 作形式主语的结构
(1) It is ＋名词＋从句
It is a fact that … 事实是…
It is an honor that …非常荣幸
It is common knowledge that …是常识
(2) it is ＋形容词＋从句
It is natural that… 很自然…
It is strange that… 奇怪的是…
(3) it ＋不及物动词＋从句
It seems that… 似乎…
It happened that… 碰巧…
(4) it is＋过去分词＋从句
It is reported that… 据报道…
It has been proved that… 已证实…
3. 主语从句不可位于句首的五种情况
(1) if 引导的主语从句不可居于复合句句首。
(2) It is said , (reported) …结构中的主语从句不可提前。例如：
It is said that President Jingo will visit our school next week.
(3) It happens…, It occurs… 结构中的主语从句不可提前。例如：
It occurred to him that he failed in the examination.
(4) It doesn’t matter how/whether …结构中的主语从句不可提前。例如：
It doesn’t matter whether he is wrong or not.
(5) 含主语从句的复合句是疑问句时，主语从句不可提前。例如：
Is it likely that it will rain in the evening?
4. What 与that 在引导主语从句时的区别
What 引导主语从句时在从句中充当句子成分，如主语．宾语．表语，而that 则不然。例如：
What you said yesterday is right.
二：宾语从句的几个特征：1、引导词：what\which\whose\when\whether\if\where
2语序：宾语从句必须是用陈述语句。
如：I think that you must work harder.
宾语从句的引导词、连接词的区别、否定转移等现象。
(1)表达时间的几个句型：一般用when或者是what time：
What time will the train leave?
由于时刻都是固定的，也可以用一般现在时代替一般将来时：
What time does the train leave?
(2)时间的表达方式：8：19(nineteen past eight),7:57(three to eight)，在时间的中间也可以加上分的单词(minutes)
(3)had better +动词原型。意思是提要求，建议。但是上下级不能用这种方式，因为语气太重：
You had better give up smoking .
(4)sb leave sth +地点
I left my book in my classroom yesterday.
(5)may I have your name(address\age)?一般询问对方的年龄、名字等，不要习惯以前的问法，这样很不礼貌，而是要采访上面的问法。以前的习惯是：how old are you? \what's your name?
(6)修饰名词的代词次序：限-描-大-形---年---颜----籍----物--------类+名词：
this is a bridge.
This is a beautiful bridge
补充：从句的语序永远是陈述句。
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