Final answer:
Money received for mowing a lawn acts as a medium of exchange, enabling the easy trading of services for goods or other services.
Step-by-step explanation:
Receiving money as payment for mowing your neighbor's lawn best illustrates the function of money as a medium of exchange. When money acts as a medium of exchange, it is used to facilitate the buying and selling of goods or services. In this case, the money serves as an agreed-upon means for you to sell your lawn-mowing service and in turn, gives you the ability to purchase goods or services from someone else.