Final answer:
The gold standard was the system where the U.S. dollar's value was directly tied to gold reserves. It provided stability but limited economic flexibility. This system was ended by President Nixon in 1971. The correct option is the C. gold standard.
Step-by-step explanation:
The system of tying the value of the U.S. dollar to the amount of gold held in U.S. reserves was known as the gold standard.
The adoption of this standard meant that the currency’s value was directly linked to the amount of gold held by the government, providing a stable exchange rate.
However, it also restricted economic flexibility, as the amount of money in circulation was limited by the gold reserves. In 1971, President Nixon ended the gold-based system, which marked the beginning of fiat money where the currency's value is not based on physical commodities, but rather on the trust and authority of the issuing government. The correct option is the C. gold standard.