Jason wants to conduct an experiment to test whether eating broccoli every day improves the mood of undergraduate students. Which experimental design should he choose? Question 3 options: A) A group of his close friends that he knows are usually in a good mood after eating broccoli. B) A group of randomly chosen high school students that he randomly assigns to either the control or experimental group. C) A group of randomly chosen undergraduate students that he screens for vegetable preference, only selecting those who enjoy eating broccoli. D) A group of randomly chosen undergraduate students that he randomly assigns to either a control or experimental group