Given the equation of exchange set forth by the quantity theory of money (M x V = P x Q), where M is the supply of money, V is the velocity of money, P is the price level, and Q is real output, which of the following best defines M?
A. The total amount of currency, coins, and banking sector.
B. The quantity of goods and services produced within an economy.
C. The average number of times a dollar is spent in a given time period.
D. The average of level of prices for a given basket of goods.