Final answer:
Money serving as a means of exchange is exemplified when purchasing common stock by writing a cheque.
Step-by-step explanation:
The act of purchasing common stock by writing a cheque best exemplifies money serving as a means of exchange. This is because the individual is using money to facilitate the exchange of the common stock with the payment instrument being a cheque.
Money serves as a medium of exchange when it is used to purchase goods, services, or financial assets like common stock.