What are discretionary calories?

a: the difference between the number of calories needed daily and the number eaten that day to fulfill nutritional requirements

b: the difference between the recommended daily number of calories and the actual calories consumed on food items that are not in a food group on the food plate

c: the recommended number of calories minus the actual calories consumed from the food groups on the food plate

d: the recommended number of calories a person should consume daily from the food groups on the food plate