The correct answer is B.
The Federal Reserve is the United States Central Bank. It is in charge of designing and implementing the monetary policy, which is a mechanism that allows a central bank to intervene in the economy of a country by modifying the interest rates and the amount of money in circulation, denominated money supply.
These instruments of the monetary policy allow the Fed to influence investment and, therefore, aggregate demand levels, and to stabilize price levels and, hence, inflation.