Final answer:
Money serves as a medium of exchange, unit of account, and store of value.
Step-by-step explanation:
Money serves several functions: a medium of exchange, a unit of account, and a store of value. In the first scenario, Sondra's money in her checking account can be used to buy things, making it a medium of exchange. In the second scenario, Sondra can compare the prices of different items using money as a unit of account. In the third scenario, Sondra writes a check, which is a form of money used as a medium of exchange.