Dr. Henrietta Bootsma designed and produced a 30 second radio commercial for a local automobile dealer. Next, she had the three most widely listened to radio stations in town play the commercial 15 times a day, every day, for two weeks. She waited until the end of the two-week period, then she called Jack to see what his sales had been lately. What experimental design did she use? Choose from the following possible choices the correct answer: (A) one-shot case study. (B) classical experiment. (C) static group comparison. (D) time series