please help with this question

If the banking system in the United States was a 100% reserve banking system (all demand deposits are held in reserves), what tools would the Federal Reserve have to control the money supply? a. Reserve requirement ratios but not discount rate/federal funds rate or open market operations. O b. None of these c. Open market operations but not reserve requirement ratios or discount rate/federal funds rate. O d. None since banks cannot lend money. e. Discount rate/Federal funds rate but not open market operations or reserve requirement ratios