What Kind of Impact Do Superdelegates Have on the Selection

What kind of impact do Superdelegates have on the selection of the Democratic presidential nominee?

A) None: they are allowed to attend the convention but cannot vote.
B) Superdelegates would lose legitimacy if they decided a nomination at the convention, but their endorsements still have a large impact in the ""invisible primary.""
C) Superdelegates make up 20% of all delegates and have decided the Democratic nominee at the convention in several nomination contests.
D) Superdelegates have little influence because they are unwilling to go against the primary winner.