Acurrency is a system of money created and used by a. an individual or a group of people b. all people who live in the same era. c. a nation or region of the world. d. a town, city, or state within a region.

Your question is asking what specific people/group of people use the currency system.

The reason why answer choice "C.) A nation or region of the world" would be the correct answer because currencies are used in a nation or region in order to buy/purchase things within the place. A currency is a specific money that is accepted in a country; also being able to use that currency around the whole country to buy/purchase things. The value of the currencies could be different for different countries; most of the countries or nations in this world have different values in currencies.

The currencies values are different in each country because each country has a different success in their trades. When a countries exports trades prices are higher than the import trades, then their country's currency would be more valuable. The value of the currency all depends on their performance in trades.

(Example for currency value) For example, 1 Kuwaiti Dinar (KWD) currency is worth 3.29 in USD, which means that the country is very successful in trades, and people in the country uses that currency.