Fifty volunteers were alphabetically divided into two equal groups, Group A to participate【C1】______a 7-week exercise program, and Group B to avoid【C2】______exercise of any sort during those 7 weeks. On the day before the exercise program began, all 50 men participated in a step-test. This【C3】______of stepping up and down on a 16-inch bench【C4】______30 steps a minute for 5 minutes. One minute after completion of the step-test the pulse【C5】______of each subject was taken and recorded. This【C6】______as the pretest for the experiment. For the next 7 weeks, subjects in the experimental group(Group A)r°de an Exercycle(a motor-driven bicycle-type exercise machine)for 15 minutes each day. The exercise schedule【C7】______for riders to ride relaxed during the first day's ride,【C8】______jholding on to the handle bars and foot pedals【C9】______the machine moved.【C10】______, for the next 3 days, they rode relaxed for 50 seconds of each minute, and pushed, pulled, and pedaled actively for 10 seconds of each minute. The ratio of active riding was【C11】______every few days,【C12】______by the third week it was half of each minute, and by the seventh week the riders were【C13】______15 solid minutes of active riding. 【C14】______end of the 7 weeks, the step-test was again【C15】______to both groups of subjects, and their pulses taken. The post-exercise pulse rates of subjects in the experimental group【C16】______found to have decreased a(n)【C17】______of 30 heart beats per minute, with the lowest decrease 28 and the highest decrease 46. The pulse rates of subjects in the control group【C18】______the same or changed no more than 4【C19】______, with a(n)【C20】______difference between the initial and final tests of zero."