Option 1: Medium of exchange -> This is a function of money itself, used to facilitate transactions.
Option 2: Barter exchanges -> Direct exchange of goods and services without using money as an intermediary.
Option 3: Unit of account -> A function of money that provides a common measure of value.
Option 4: Store of value -> A function of money that allows it to retain purchasing power over time.
Hence, Option 2: Barter exchanges -> Barter is an ancient system of exchange where goods and services are directly traded for other goods and services without using money. For example, exchanging wheat for cloth, or labor for food. This was the primary method of trade before the invention of money. The main limitation of barter is the requirement of a 'double coincidence of wants' - both parties must want what the other has to offer. -> correct