Money is a medium of exchange when:

a. it is used to facilitate trade between buyers and sellers.

b. it is used to transfer wealth from the present to the future.

c. it is used to communicate the market value of goods and services.

Money is a medium of exchange when: it is used to facilitate trade between buyers and sellers.

a. it is used to facilitate trade between buyers and sellers.

Explanation:

Money is a medium of exchange when there is a need trade between the buyer and seller. It is the medium of exchange.

The buyer will buy something from the seller and in return will exchange money which the seller will further use to buy something that he needs.

Therefore, Money is considered as the source of income and is considered as a medium through which exchange activities can take place.