Which of the following statements concerning budget preparation is incorrect?

a) Flexible budgets are prepared for multiple levels of activity.

b) If a participative approach is used to prepare budgets, only top management is involved in the budgeting process.

c) The preparation of the sales budget is the starting point in the budgeting process for manufacturers.

d) Participative budgeting increases the risk that employees will create budgetary slack.

e) A zero-based budgeting approach requires that every number in the budget be justified from "the ground up."