1.楼主应该是忘记了在fish后面加上一个逗号. 正确的写法和答案是：The cat likes fish,(as) is known to us. 2. 1）非限制性定语从句中,关系代词as代替整个主句the cat likes fish,做该定语从句的主语(从句). 即完整的定语从句为：(That the cat likes fish) is known to us. 猫喜欢鱼（这种情况）是我们所知道的. 2）整个句子可以翻译成：就像/正如我们所知道的那样,猫喜欢鱼. 2）which虽然也有上述用法,但是关系代词做主语,而其后是be动词时,只能用as,而且which不可以翻译成as所具有的“正如/就像...一样”的含义.
