1)He is the man who/whom/that i talked about. 2)He is the man about whom i talked.
1)it is the a problem which you know noting of. 2) it is a problem of which you konw nothing of.
非限定性定语从句
1.1)与限定性定语从句的区别.(意思) :The house which she bought last year has been given away.限定名词"房子”是去年买的。 :The house,which she bought last year,has been given away.(对房子的补充说明)
2.非限定性定语从句:As"正如......" 1)as多为固定搭配,“正如”位置:句前、句后、句中 对比:which引导的句子只能在先行词/主语之后。 as is often the case。(通常就是这样) as often happens(事情往往如此) as is know to all (众所周知) as might be expected(正如所预料的那样) as has been said before(如前所述) as is mentioned above(正如上面所提到的