选 As
译为：众所周知,马克吐温是世界知名作家.
As is know to 固定结构,像短语一样,但要注意区分
that:
That mark twain is a great writet is know to all of us
it:
it is said that mark twain is a great writetr.
译为：据说马克吐温是个大作家.
whick 肯定不对,连边都不沾,马克吐温是个人,怎么能用whick,可用who改
mark twain who is known to the world is a great writer.