Which of the Following Is an Example of the Use

Which of the following is an example of the use of money as a medium of exchange?

A) Dave keeps $250 in his drawer for a "rainy day."
B) Mike gets a friend to give him a beer today in return for promising to give the friend two beer when Mike gets paid at the end of the month.
C) Judy lends her car to a friend who signs a promissory note that she will pay Judy $10 a day for the use of the car after she returns the car to Judy.
D) Barry pays $275 with his bank debit card for tickets for an NHL play-off game.
E) ABC Investments Inc.enters in its account books that it owes Nallai $20 for his last month's investment income.