Answer: A. gold standard
Explanation:
When using the gold standard, the value of the currency of a country is based on the value of gold. This means that the currency will be able to buy a fixed amount of gold thereby enabling it to be exchangeable in banks both abroad and at home.
Banks would therefore be required to exchange the currency (U.S. Dollars) for that fixed amount of gold that the country has set its currency at. This currency standard has largely been abandoned.
