Which of the following is true of budgetary slack?

a$.$ It reflects operating realities such as actual level of activity, seasonal variations, and general economic trends.

b$.$ It occurs when top management simply obtains formal acceptance of the budget from subordinate managers without seeking real input.

c$.$ Budgetary slack occurs when a manager deliberately underestimates revenues or overestimates costs in order to make budgeted expectations more easily achievable in the future.

d$.$ Budgetary slack occurs when top management has total control of the budgeting process, allowing only superficial participation from lower$-$level managers.

e$.$ None of these choices are correct.