Answer: d. all of the above
Step-by-step explanation:
If the Federal Reserve wanted to increase the money supply, they could use all the monetary policy tools listed.
Using Open Market operations, they could buy securities from the public and by paying for those securities, they would inject money into the economy. This is how Quantitative Easing works as well.
They would also reduce the reserve requirement or reduce the discount rate as well. The former would allow banks to be able to loan out more money and the latter will make it easier for banks to borrow from the Fed both of which will increase how much banks can inject into the economy.