You are developing a class library. Portions of your code need to access system environment variables.
	You need to force a runtime SecurityException only when callers that are higher in the call stack do not have the necessary permissions.
	Which call method should you use?()
	A.set.Demand();
	B.set.Assert();
	C.set.PermitOnly();
	D.set.Deny();
 
                            