The sun heats the earth, _____ we all know

如果 非要说的话，你记住

as引导非限制性定语从句既可放在主句之前，也可放在主句之后，用来修饰整个句子。通常用下列句型：as is known to all, as is said, as is reported, as is announced, as we all know, as I expect 等。
e.g. As I expected, he got the first place again in this mid-term examination. 正如我所预料的那样，他在这次期中考试中又获得了第一名。

所以 以后看见as is known to all, as is said, as is reported, as is announced, as we all know, as I expect 这些的时候 用as 记住好了，特别喜欢考

希望帮到你

这是个比较特殊的定语从句，as看做关系代词，代指的是其后整句话的内容。
“as”特殊定语从句的位置较灵活，可以置于先行成分之前、之中或之后。
“as”特殊语从句常用一些表示“合乎自然规律”、“众所周知”或“经常发生”等意义的词语，如natural, known to all, usual等。

A，which只能做疑问代词和形容词而不能做副词，as可以作副词，希望对你有帮助

as在引导非限定性定语从句时，有“正如”的意思