OG52 why no D?

52. Most consumers do not get much use out of the sports equipment they purchase. for example, seventeen percent of the owners job more than once a year, and only severnteen percent job more than once a week.

Which of the following, if true, casts most doubt on the claim that most consumers get little use out of the sports equipment they purchase?

C. Many consumers purchases jogging shoes for use in activities other than jogging

D. Consumers who take up jogging often purchase an athletic shoe that can be used in other sports.

Why not D?

D-- Althletic shoes, as jogging shoes, are sport equipment, so we consider them irrelevant. If consumers use an athletic shoe not only for jogging but also for other sports, we cannot conclude that people make a lot use of the sport equipments? --> doubt the conclusion that most consumers get little use out of the sports equipment.

OG explaination of D: most likely to be among those who frequently use sports equipment and whose existence the argument concedes. ( already agree that these people frequently use sport equipment, but why argument concedes cannot casts doubt?)

老大，我觉得您可能没把OG的答案解释看全。OG的解释原文为：

Because the consumers (mentioned in D) and joggers (mentioned in E) mentioned in D and E respectively are most likely to be among those who frequently use sports equipment and whose existence the argument concedes, D and E are inappropriate.

所以，whose existence the argument concedes指的是E中的joggers。而E中的joggers，又的确在题干中出现，因此原题本身实际已经承认这部分人买了运动器材又经常使用，当然不可能再cost doubts啦。哪有搬起石头砸自己脚的呢？