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　　北京高中英语资料网：高中英语重要语法

　　虚拟语气在各种从句的应用

　　主语从句的虚拟

　　1. It is + adj. + that sb. (should) do

　　常见的形容词有：necessary, important, strange, natural

　　It's important that he take my advice.

　　2. It is + n. + that sb. (should) do

　　常见的名词有：a pity, a shame, no wonder, one's wish

　　It's a pity that he be so silly.

　　3. It is + done + that sb. (should) do

　　常见的过去分词有：suggested, advised, demanded, requested, required, asked, ordered,

　　proposed, decided, desired, insisted等。

　　It's requested that she go home as soon as possible.宾语从句的虚拟

　　1. 表命令，表建议，表要求的动词，后接宾语从句虚拟。虚拟的构成为(should) do。

　　I advise that he stay at home.

　　2. wish后接从句，虚拟的构成是往过去推一个时态。

　　I wish I had watched the football match last night.

　　注意以下几组词或短语用于虚拟语气中。

　　1. as if, as though

　　He speaks English as if he were a native speaker.

　　2. otherwise, but, even though

　　He was ill. Otherwise he would have been there.

　　3. with, without, but for

　　Without your help, I would have died two years ago.

　　But for your help, I would have died two years ago.

　　4. would rather I'd rather you told me yourself.

　　5. It's time that

　　It's time that you went to bed.

　　It's time that you should go to bed.

　　表语从句中的虚拟

　　在表语从句中，表示间接的命令，要求、请求、建议、决定等，主句中的主语通常是suggestion, proposal, request, orders, idea等。从句谓语形式是"(should)+动词原形"。如：

　　His suggestion is that we (should) leave at once.

　　名词从句部分：

　　1. that不可省略的情况

　　2. that引导同位语从句和that引导定语从句的区别：同位语从句中的that是连词，不做成分，只连接主从句，不能省略;定语从句中的that要代替先行词在从句中做主语、宾语或者表语，并且做宾语时可以省略。从语义上看，同位语从句是对前面名词的解释、说明或内容;而定语从句时对前面名词的限定。

　　We should consider the students’request that the school library provide more books on

　　popular science. (that引导同位语从句)

　　The only hope that he expressed was that they would do what they could to help the people

　　in disaster areas. (that引导定语从句)

　　3. 要根据句子结构尤其是谓语动词判断从句的类型：

　　What is known to us all is that the 2008 Olympic Games took place in Beijing.

　　本句含有一个主语从句和一个表语从句，主句的动词为is。

　　It is known to us all that the 2008 Olympic Games took place in Beijing.

　　本句含有一个主语从句，主句的动词为is known to。

　　As is known to us all, the 2008 Olympic Games took place in Beijing.

　　本句含有一个定语从句，主句的动词为took place，as引导非限制性定语从句。

　　4. 名词性从句的语序和语态。

　　名词性从句均应用陈述语序，不能用疑问语序，其时态应该和主句时态保持一致。

　　5. 名词性从句中连词的省略。

　　介词后的连词以及引导主语从句和同位语从句的连词不可省略。that引导名词从句(除了引导先进个宾语从句可省略外)都不可省略，但是引导定语从句并在从句中做宾语时可以省略。

　　that不能省略的情况：

　　1)介词后面的that不能省略：

　　Peter is a good student except that he is sometimes careless.

　　2)当that引导的宾语从句位于句首时：

　　That he ever did such a thing I don’t believe.

　　3)主句谓语动词和that从句之间有插入语，that不省略：

　　She said that, if she failed, she would try again.

　　4)当宾语从句有其他从属连词时，that不省略：

　　He told me that if it was necessary they would work extra time.

　　6.名词性从句中it的使用：

　　为了保持句子平衡，多数情况下，it作形式主语或形式宾语，将真正的主语或宾语从句后置。

　　定语从句

　　关系代词有who, whom, whose, which, that, as,和关系副词when, where, why。

　　(1)that指物时一般可与which互换，但在下列情况下，要用that而不用which。

　　a. 先行词有all, everything等不定代词时，如，

　　Everything (that) he did is wrong.

　　b. 先行词被all, every, no, some, any, little, much等修饰时，如，

　　I'll read all the books (that) you lend me.

　　c. 先行词被序数词或形容词更高级修饰时，

　　This is the first letter (that) the boy has written.

　　d. 先行词被the only, the very, the same, the last修饰时，如