Astudent conducts an experiment to see how music affects plant growth. the student obtains four identical plants. each one is potted in the same type of soil and receives the same amount of sunlight and water each day. plant a listens to classical music for three hours each day. plant b listens to rock music for three hours each day. plant c listens to country music for three hours each day. plant d does not listen to any music at all.4. in the experiment described in the scenario, which group represents the control group?