What "backs" the money supply of the U.S.?

Question

Quizplus · Accepted Answer

The U.S. government's ability to keep the value of money relatively stable is ultimately what backs the money supply. The value of money is supported by the confidence that people have in the stability of the U.S. government and its economic policies.

Answer: C
 The Federal Reserve System is responsible for issuing currency and regulating the money supply, which ultimately backs the U.S. money supply. However, this is only possible because of the stability of the U.S. government and the trust people have in the U.S. financial system.

Answer: D
 The intrinsic value of coins is typically less than their face value (e.g. a penny costs less than one cent to produce), not greater. Therefore, D is not the best choice.

What "Backs" the Money Supply of the U.S