Answer:
A) a medium of exchange.
Explanation:
One fundamental feature of money is its use as a medium of exchange. Sellers of commodities are to exchange their commodities for a particular monetary sum.
This sum is the monetary value of the items as determined by the seller.
As a unit of accounting, money is used to compare the value of one item or commodity to another.
As such, the price tag of $4 for a portable power bank is an example of money as a medium of exchange.
