On the spending side, what is the main big-picture challenge for anyone trying to balance the federal budget? Question 12 options: a) There is no big challenge on the spending side, just on the revenue side. b) the growth of discretionary spending as a percentage of the overall total c) the growth of mandatory spending as a percentage of the overall total d) the growth of interest on debt as a percentage of the overall total e) the uncertainty caused by frequent legislative changes in spending policy