Final answer:
The best completion of the definition of money as used by economists is 'd. All of the above', since money serves as a medium of exchange, a store of value, and a unit of account.
Step-by-step explanation:
The question 'Which of the following best completes the definition of money as used byeconomists?' relates to the functions of money in an economy. Economists define money by several functions: it acts as a medium of exchange, a store of value, and a unit of account.
As a medium of exchange, money is widely accepted to buy and sell goods or services. Instead of bartering with a direct exchange of goods, money simplifies transactions. As a store of value, money can be saved for future use while maintaining its worth, ensuring that it can be spent later. The unit of account function allows goods and services to be priced in a uniform manner, facilitating comparisons across them.
Therefore, the best completion of the definition of money as used by economists is 'd. All of the above', as money serves all three purposes.