Which of the Following Combinations Would Unambiguously Decrease the Supply

Multiple Choice

Which of the following combinations would unambiguously decrease the supply of money?

A) ​The Fed pays a lower interest rate on bank reserves and increases the required reserve ratio.
B) ​The Fed conducts an open market purchase of government securities and raises the discount rate.
C) ​The Fed pays a higher interest rate on bank reserves and conducts an open market purchase of government securities.
D) ​None of the above would unambiguously decrease the supply of money.