The answer would be A. <span>Christians must confess that is God is good and that God's "mercy endureth forever."</span>
The main clause here is The man autographed copies of it at the bookstore. This means that the subordinate clause is what is left - who wrote this new and popular book.
The subordinate clause functions as an adjective, which means that it describes the subject <em>the man. </em>
