Explanation:

- Legal Money: Generally refers to money that is recognized by law for the payment of debts. This often overlaps with "fiat" but highlights legal recognition.

- Fiat Money: This is money that has value because a government maintains it and declares it to be legal tender. It is not backed by a physical commodity but by the authority of the government.

- Authorized Money: Could refer to any money that is officially sanctioned by the government but is not a common standard term like "fiat."

- All of These: This implies that all options are the same, which they are not.

Therefore, "fiat money" is the best description for money backed by governmental authority.