All of these are ways in which the federal reserve system can a) control the stock market. b) regulate the money supply. c) decrease consumer spending. d) challenge presidential power.

B) regulate the money supply.

Explanation:

The question is incomplete, however, I can give you a general context, and an answer.

The main function of the Federal Reserve is to control inflation.

From the 1980s, monetarism, an economic school of thought that advocates for low inflation, and a stable money supply, has come to dominate, not only the actions of the Fed, but also the actions of most central banks in the world.

Before Monetarism took hold, Keynesianism was more relevant, and it argued for the use of expansionary monetary policy to reduce unemployment. This keynesianist era lasted from the 1930s until the 1970s, when an economic period known as Stagflation occurred in the United States and Western Europe. In Stagflation, both inflation and unemployment are high, and economic growth is low.

Stagflation forced the Fed to adopt Monetarism, and abadon Kenynesianism as the guiding theory to its actions.

However, whether a central bank is monetarist or kenynesianist, its primary function is to regulate the money supply. A keynesianist will probably expand the money supply more rapidly than a monetarist, but they are both controlling the money supply, hence, the correct answer is B)