DrPena Wants to Investigate Whether Children Who Eat a Lot

Dr.Pena wants to investigate whether children who eat a lot of processed sugar find it more difficult to sit still and concentrate in school than children who don't.She randomly divides all the children in the Edward L.Thorndike Elementary School into two groups.Group one is given a breakfast of Chocolate Frosted Sugar Bombs cereal and chocolate milk,and a midday snack of Jolt Cola and Crunchy Sugar Granola Chews.Group two is given an identical breakfast and snack,but their food contains artificial sweeteners instead of processed sugar.Dr.Kieu records the behavior of each group of children on these diets for one month,and compares them statistically.In this experiment,Dr.Pena's control group variable is

A) the children's behavior before and after their breakfasts and snacks.
B) the type of sweetener used in the children's breakfasts and snacks.
C) the children in group one.
D) the children in group two.