定语从句（一个句子）

Antarctic about which we know very little is covered with think ice all the year round.

其中about which做什么成分啊，主语？状语？宾语？还是什么别的？？

KNOW ----ABOUT STH ,这是个词组，对于某事知道得少或多

which 是先行词 know about 是个短语 此处把about 提前了 about which we know very little 都是定语

是定语从句的连接词， which we know very little about 的宾语是 Antarctic，而 Antarctic 又是 is covered with think ice all the year round的主语。这句是典型的定语从句。which we know very little about 是做 Antarctic的定语。这句话的意思是：我们了解甚少的南极洲常年被冰雪覆盖。