請教這句英文的代名詞?

everyone accepts the fact that (it suerly is........)

( )中是形容詞子句,所以前面要多加that.

另外,that是關係代名詞沒錯

引導形容詞子句的附屬連接詞（關係代名詞）有：that, who, which, whose, whom,（that 可替代主格和受格的代名詞，that = who, which, whom）。
 

which talks about human nature 是肯定句,並沒有倒裝啊

倒裝通常是用在疑問句.