Question

They've invited me to their party,____is kind of them.

They've invited me to their party,____is kind of them.
A.this B.that C.which D.as
答案是C，讲解说which作从句主语，译成：“这一点”
但是，书上写which作主语时，用于“主语+谓语+宾语（+补语）”或被动结构，它接近于并列结构，相当于and it/this/that。
as作主语时，仅用于“主语+系动词+表语”，不与主句抵触。
我选的是D

Answer 1

which引导非限定性定语从句时有一个特殊用法, 即它所引导的非限定性定语从句修饰主句中更多的部分甚至整个主句(这时被定语从句所修饰的“先行词”要作广义理解), which仍在定语从句中作主语、 宾语或表语。例如:
They have invited us to their party, which is very kind of them. 他们邀请了我们参加聚会,他们真的很好。
把非限定性定语从句“which is very kind of them”的先行词视为主句中的“the party”显然不符合整句的语境, 被“which is very kind of them”所修饰的是整个主句, which所引导的这类特殊的非限定性定语从句对主句所叙述的情况进行某种意义的补充说明, which常可译为“这一点, 这件事”。
望楼主采纳:-)