Final answer:
The correct answer is option c) a medium of exchange.
Step-by-step explanation:
Money serves as a critical tool for facilitating trade and commerce. The question asks about the role of money as a medium of exchange, which simplifies comparisons of the value of goods and services by providing a common measure. When money is used in this capacity, transactions become much more efficient than in a barter system, where a double coincidence of wants is required. The various functions of money include serving as a medium of exchange, a unit of account, a store of value, and a standard of deferred payment.
There are different types of money, such as commodity money, which has intrinsic value (like gold or silver), and fiat money, which is declared legal tender by a government but has no intrinsic value. Comparisons of value are easiest when money is used as a medium of exchange because it is widely accepted and facilitates trade without the need for direct bartering of goods and services.