(6)as引导的定语从句:
①as用作关系代词和关系副词引导限定性定语从句,并在从句中作主语、表语或状语,构成the same...as,such...as等结构。例如:I like the same book as you do.(as作宾语)I shall do it in the same way as you did.(as作状语)I want to have such a dictionary as he has.(as作宾语);
②as引导非限定性定语从句。as在定语从句中作主语、表语或宾语,这个定语从句说明整个句子,可以放在主句之前。例如:
As we all know,he studies very hard.
(as代表整个句子,作宾语)
As is known to all,he is the best student in our class.
(as代表整个句子,作主语)
The experiment is very important,as indeed it is.
(as代表整个句子,作表语)
常用的这种类似插入语的句式有as is said above,as already mentioned above,as is known to all,as it is,as is often the case,as is reported in the newspaper等。
注意:①关系代词在从句中作主语时,从句的谓语动词的人称和数必须和先行词保持一致;
②关系代词whom,which,that在限定性定语从句中作动词宾语或介词宾语,而该介词又位于从句末尾时,经常省略,但as一般不省略;
③关系代词which和as在定语从句中的区别是:which不能放在句首,而as则可以;在句中时,as有"正如"、"就像"之意,而which则没有此意。
