Answer:
C) voluntary exchange
Explanation:
In economics, voluntary exchanges take place when a buyer and a seller both freely and willingly decide to trade their products or services. Before modern money become so widely used, the barter system was used to exchange mostly goods.
The whole idea behind a voluntary exchange is that both the seller and the buyer will be better off by carrying out the exchange transaction, i.e. I buy something because it satisfies my needs, and it will make me feel better.
