Choice "C" is correct. The master budget is based on one production level and a flexible budget is designed to reflect any production level within a relevant range of production activities.Choice "d" is incorrect. The flexible budget is used before and during the budget period.Choice "b" is incorrect. The flexible budget is based on fixed standards which are appropriately developed for the relevant range of production activity.Choice "a" is incorrect. The flexible budget is developed for single departments and for the production facility as a whole.