副词可以作表语,定语从句中从句中,关系副词是不是不仅能作状语,还可以作表语呢?

副词可以作表语,定语从句中从句中,关系副词是不是不仅能作状语,还可以作表语呢?
the place at which he was yesterday is a brothel.at which 可以换做where吗
网上找了道类似的题目
After 3 months of sailing eastwards they arrived in Australia,a place to___ westerners had never been.
A,which
B,that
C,where
D,/
也就是说去掉to,换成where,让where作表语,