From experience, I know that:
which, who, where, why, whom, there, that
are relative pronouns but I wonder about the expressions:
'by which', 'to which', 'at which', 'to whom
Are these also relative pronouns in an adjective clause?
Example: this is the lab to which I go everyday.
Here I believe which is the only relative pronoun: not the combined words to which. I think that to is just a preposition modifying the relative pronoun meaning.