Analyze the sentence to determine the main clause and the subordinate clause. Then choose the function of the subordinate clause.

The man who wrote this new and popular book autographed copies of it at the bookstore.

Main clause:

The man who wrote this new and popular book autographed copies  of it at the bookstoreThe man autographed copies of itThe man who wrote this new and popular bookThe man autographed copies of it at the bookstore

Subordinate clause:

who wrote thisThe man who wrote this new and popular bookwho wrote this new and popular book autographed copies of it at the bookstorewho wrote this new and popular book

Subordinate clause functions as a(n):

nounadverbadjective