The statement that best illustrates the difference between the U.S. dollar (a form of fiat money) and a U.S. gold certificate (a representative currency) is:
A U.S. dollar does not represent a claim to some specific asset.
Fiat money, like the U.S. dollar, has value because the government maintains it and people have faith in its value, while a gold certificate is backed by a specific quantity of gold, thus representing a claim to that asset.