Within the activity of sterilization, "defensive" purchases or sales of government securities by the Federal Reserve are

	a.	open-market operations undertaken during periods in which the United States has been at war.
	b.	open-market operations that are undertaken to prevent other factors from bringing about undesired changes in the monetary base.
	c.	open-market operations directed specifically at effecting net decreases in the monetary base.
	d.	open-market operations directed specifically at effecting net increases in the monetary base.
	e.	open-market operations directed toward initiating monetary policy