Answer: B. It allows people to buy, sell, and trade goods efficiently.
Money functions as a medium of exchange by providing a common currency that can be used to buy and sell goods and services. Money allows for efficient and convenient transactions, as it eliminates the need for bartering and reduces the risk of people not accepting a currency in exchange for goods. Money also has a value that is set by the market, rather than the government, and it can be used to compare the value of different products.