Answer: b. increases, the money multiplier decreases, and the money supply decreases
Explanation:
When the central bank raises the reserve requirement, the reserve ratio increase as banks will now hold more money as reserves. The Money multiplier decreases as Reserve ratio increase therefore when The reserve ratio increases the money multiplier will decrease which will then lead to a decrease in the money supply.
When Banks hold more money because of an increased reserve requirement, Money Multiplier and Money supply will decrease because each bank will have less funds available for loans.