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1、在名词性从句中的用法在复合句中，起名词作用的从句，称为名词性从句。根据句法功能，名词性从句可以分为主语从句，宾语从句表语从句和同位语从句。名词性从句不论是用什么词来引导，从句都必须用陈述句语序，即“引导词+主语+谓语+其它”。疑问代词或疑问副词充当引导词时，有词汇意义且在从句中担当一定的成分;whether(if只用于宾语从句)作引导词仅有词汇意义且不在句中担当任何成分;如果从句的语法成分完整，主从句语意通顺时一般就该用that来引导。 一that 用于引导宾语从句时通常可省略，尤其在口语中。而that引导主语从句表语从句同位语从句时一般不能省略。如: He told me (that) th
2、e meeting had been put off. That our volleyball team had beaten theirs pleased every one of us. The problem with building the factory is that we are lack of money. Word came that he has recovered from the bad disease. that引导宾语从句时在以下几种情况中不能省略: 1. 宾语从句为多个并列句时，前面分句的that可以省略，但最后一个分句的引导词that不能省略。如: He to
3、ld me (that) he had entered a university in Nanjing and that he was enjoying the college life there. 2. 宾语从句本身为一个复合句且复合句中的从句位于主句前时，that不能省略。 He said that if I went there， he would go too. She believes that what the teacher says must be right. 3. 主句与宾语从句加入了插入语时。 He said， in his opinion， that it was t
4、oo early for middle school students to carry cell-phones. 4. that引导的宾语从句后置，用形式宾语it代替时。 China has made it clear to the world that it is strongly against terrorism. 5. 跟在介词but， besides， except等后引导宾语从句时。 Your composition is very good except that there are a few mistakes. 二that引导主语从句可以用形式主语it来代替并将从句后置，从
5、而达到平衡句子的目的。这样的句式有: 1. Its+名词+that用于该句型的名词有a pity， a great pleasure， no wonder， (high) time等。 Its a pity that you shouldnt go with us to the concert tonight. Its high time that they started to work. 2. Its+形容词+that用于该句型的形容词有possible， necessary， important， natural， strange 等。 Its true that his brother
6、 got his left hand hurt when he was working on the machine. Its necessary that we practiced speaking English as often as possible. 3. It+不及物动词+that 用于该句型的不及物动词有happen， occur， appear等。 It happened that a doctor was on the train at that very moment. It occurred to me that I was going the wrong way. 4.
7、 Its+过去分词+that用于该句型的过去分词有said， reported， announced等。 It is said that two people got killed in the traffic accident yesterday. It is announced that China is strongly against terrorism. 三当that引导的宾语从句后接有补足语时，也习惯将从句后置，而用形式宾语it代替。即句型:主语+think/consider/find+it+补足语(形容词或名词)+that宾语从句。如: We all think it great
8、 fun that we learn English in Mr. Hus class. Mr. Green considers it important that students should form good habits of learning. 四doubt作动词时其后的宾语从句及作名词时其后的同位语从句只能用that来引导。如: We dont doubt that he is fit for this job. There is no doubt that we Chinese are determined to stop Taiwan from being separated
9、 from mainland. 五名词the reason作主语或why开头的主语从句，其后的表语从句只能用that引导，不能用because。如: The reason for coming late is that I was caught in the traffic jam. Why she kept silent about the matter is that she didnt want to be involved in it. 六that和whether都不作句中成分，区别时要从主句来寻找信息。若主句中有question， hasnt been decided， is not
10、 known yet， depends on， wonder， doubt等词语时且表示“不肯定”或事物的“两面性”时应用whether;而表示“肯定性”“单一性”则应用that。whether和if的用法区别1) whether和if常用来引导宾语从句，这时两者的含义区别很小，一般可通用。例如： I dont know whether/if they will come to help us. 我不知道他们是否来帮助我们。 I am not sure whether/if Ill have time to go with you. 我很难说我们是否有时间跟你们一起去。 上面两句无区别。但是，
11、当whether与or not连成一个词组时，whether不可换用if。例如： I dont know whether or not they will come for our help. 我不知道他们是否要来求我们支援。 【注意】若whether和or not不连在一起，在口语中可以用if取代whether，当然也可以用whether。例如： I am not certain if/whether the train will arrive on time. 我没有把握火车是否准时到达。 I dont care if/whether your car breaks down or not
12、. 我不在乎您的车是否是会出故障。此外，还有三种情况值得注意：(1)在介词后面只能用whether，不能用if。例如： This depends upon whether we are determined to do it. 这件事要看我们是否有决心去做。 It depends on whether he is ready. 这件事要看他是否有准备。 I am not interested in whether youll come or not. 你来不来我不感兴趣。 We havent settled the question of whether well renew our supp
13、lies of coal for factory. 是否要为我们工厂补充一些煤，这个问题我们还没有决定。(2)在动词不定式之前，只能用whether，不能用if。例如： He doesnt know whether to stay or not. She doesnt know whether to get married now or wait. (3)在及物运动discuss后的宾语从句中，只能用whether，不能用if。例如： We discussed whether we should make a change in our plan. 我们讨论了是不是要对我们的计划作一些修改。
14、We were discussing whether we should discuss the business with them. 2)引导主语从句时，只能用whether，不能用if。例如： It is unknown whether he will come. Whether the news is true remains a question. 3)引导表语从句时，只能用whether，不能用if。例如： What we want to know is whether he will come to speak to us tomorrow.The question is whe
15、ther they can take our advice. 问题是他们是否能接受我们的意见。4)引导同位语从句时，常用whether。例如： The question whether well build another lecture building hasnt been settled.The question whether hell come is unknown. 他是否来的问题还不知道。5)可用来引导一个否定的宾语从句，whether则不能用来引导否定的宾语从句，它表示正反两方面的选择意义比较强。例如： Tell me if it is not going to rain, please. 请告诉我明天是否不会下雨。 He considered if he shouldnt tell her the secret. 他考虑他是否不该告诉她这个秘密。6)if引导宾语从句，还可引导条件状语从句，“是否”。在容易引起混淆产生歧义的情况下，就不可用if，而须用whether。例如： Please let me know if you intend to come.这个句子有两种解释： A
