The barter system of exchange is a direct exchange of goods or services without the use of money. Let's evaluate the options provided:
a) A farmer trades a bushel of wheat for a basket of apples.
This situation best illustrates the barter system of exchange because the farmer and the person with the basket of apples are directly exchanging their goods without involving money.
b) A customer pays for groceries using a credit card.
This situation does not represent the barter system because the customer is using a credit card, which involves the use of money as a medium of exchange.
c) A student exchanges their textbook for a notebook.
This situation is not a barter system because the exchange is not a direct exchange of goods or services. It involves the use of items (textbook and notebook) as a medium of exchange.
d) A factory worker receives a monthly paycheck.
This situation does not represent the barter system because the factory worker is receiving money as a form of payment, rather than exchanging goods or services directly.
Therefore, option a) "A farmer trades a bushel of wheat for a basket of apples" best illustrates the barter system of exchange.