First-grade students are randomly divided into two groups. One group is given a fruit and vegetable for lunch; the other is given candy for lunch. After lunch, each group is given an attention test to compare hyperactivity. Choose the correct description of the study. A. The study is an observational study because the researchers control one variable to determine the effect on the response variable. B. The study is an experiment because the study examines individuals in a sample, but does not try to influence the variable of interest. C. The study is an observational study because the study examines individuals in a sample, but does not try to influence the variable of interest. D. The study is an experiment because the researchers control one variable to determine the effect on the response variable.