Answer:
The answer is B. changes in the quantity of money and the interest rate
Step-by-step explanation:
Monetary policy is the central bank activities that are directed towards influencing the quantity of money and credit which interest rate affects in an economy.
Through the setting of interest rate, a central bank can manipulate the amount of money in the money market which will affect the overall spending. If central bank increases interest rate, commercial bank will increase their interest rate too, people and business will be discouraged from borrowing from bank and this makes spending reduce.
Also, the central bank can control the quantity (supply) of money by engaging in open market operation. For example, if it wishes to increase the supply of money, it will buy government bond from the commercial banks.