第十章名词性从句
第十章名词性从句
一、主语从句
主语从句的连接词有从属连词if, whether, that;连接代词what, who, which, who, whatever, whichever:等;连接副词when, where, why, how等。
1.that引导的主语从句
that只起连接作用，在从句中不作任何成分，也无具体意义，通常不能省略。
△That everything in the world changes was often a theme in poetry of the Romantic Movement.
2. whether/if引导的主语从句
whether/if意为“是否”，在从句中也不作成分。whether引导的主语从句置于句首、句尾均可，但if引导的主语从句只能置于句尾，前面需用it作形式主语。
△Whether you can succeed or not depends on how hard you work at it.
△If is unknown whether/if he has agreed to my plan.
3. wh-类连接词引导的主语从句
wh-类连接词不但起连接作用，还在从句中作成分。连接代词在从句中作主语、宾语、表语、定语等，连接副词在从句中作时间、地点、原因、方式等状语。
△Why they suddenly disappeared still remains a mystery.
△Who goes light travells fast.
4.it作形式主语的常用句型
有时常把主语从句移到句末，用it作形式主语。比较常见的句型有:It+be+形容词(important, likely, possible, clear等)+主语从句;It+be+名词(fact/idea/mystery/pity/pleasure/wonder等)+主语从句;It+be+过去分词(known/said/reported/suggested 等)+主语从句;It+不及物动词(appear/em/happen等)+主语从句。
△It is not clear why he went to London.
△It is common knowledge that the whale is not a fish.
△It has been predicted that mobile phones might soon replace our wallets.
△It happens that he can understand a little about the language.
二、宾语从句
1.宾语从句的连接词
宾语从句的连接词主要有从属连词if, whether, that;连接代词what，who, which, who, whatever等;连接副词when, where, why, how等。
△He suggested that they leave the hotel at once.
△The book will show you what the best CEOs should know.
方瑶△Have you determined whichever you should buy, a Motorola or Nokia cell phone?
2.介词后的宾语从句
介词后通常跟whether或wh-类连接词引导的从句。除在except, in, besides, but后，that引导的从句一般不直接作介词的宾语，如果需要，多用it作形式宾语，然后再接从句。
△He/She only cares about whether the eyewitness has given true information
△He would have helped us but that he was short of money at that time.
3.可以用形式宾语it替代的宾语从句
(1)如果宾语从句后跟有补足语，常用it作形式宾语，而把宾语从句置于补足语之后。
△I think it necessary that we take plenty of hot water every day.
△I feel it a pity that I haven’t been to the get-together.
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(2)有些动词如hate, like, take, own, have等后跟宾语从句时，需要在宾语从句前加it。
△I hate it when they talk with their mouth full of food.
△When you start the engine, you must e to it that the car is in neutral.
4.不能省略that的情况
比熊怎么养
that引导宾语从句时，通常可以省略，但在下列情况下一般不能省略:that从句被短语、词组等与谓语分隔开来时;that从句紧接在间接宾语之后时;当it作形式宾语，后接that引导的宾语从句时;that引导的从句位于句首时;在
桂花树怎么养才长得好except, besides, in等介词后时;有多个that引导的从句时，只有第一个that可以省略;that引导的名词性从句与另一名词性从句作并列宾语时。
△The teacher advid us that to we should pay more attention reading and writing.
△I don’t think it polite that they left without saying thanks to us.
△He also likes playing the piano besides that he is good at playing basketball.
三、表语从句
表语从句的连接词主要有从属连词whether, that;连接找词what, who, which等;连接副词when, where等。此外，表语从句还可用as if, as though, becau等引导。if不引导表语从句。
△Another important difference is whether schools are state schools or private schools.
△This is why I think my happiest days will be in the future.
△It sounds as if you are from the south of the United States.
注：如果主句主语是reason，表语从句应用that连接，不能用why或becau。
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四、同位语从句
同位语从句常置于belief, doubt, hope, information等表示抽意义象的名词之后，说明其具体内容，多由that, whether, who, what, when, where等引导。
△I’ve got a feeling that one day he’ll be famous.
△The problem, why you are going to give up the plan, has not been answered yet.
注：在表示“建议、命令、要求”的名词，如suggestion, proposal, advice等后的表语从句和同位语从句需用虚拟语气，谓语动词用“( should+ )动词原形。”
五、名词性从句需要注意的几点问题
Whether和if的用法区别三十六洞天
△It all depends on whether they will support us.
△I want to know whether or not the train goes to King Street.
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2.what和that的用法区别
蒸鱼豉油
引导名词性从句时，what在从句中要充当句子成分,表达一定的含义;that在从句中不作成分也无意义，只起连接作用。
△May we ask what you’re doing in this country and what your plans are?
