OG12-CR94 关于逆否命题和双重否定的疑问

94. Studies in restaurants show that the tips left by customers who pay their bill in cash tend to be larger when the bill is presented on a tray that bears a credit card logo. Consumer psychologists hypothesize that simply seeing a credit-card logo makes many credit card holders willing to spend more because it reminds them that their spending power exceeds the cash they have immediately available.
Which of the following, if true, most strongly supports the psychologists’ interpretation of the studies?
(A) The effect noted in the studies is not limited to patrons who have credit cards.
(B) Patrons who are under financial pressure from their credit-card obligations tend to tip less when presented with a restaurant bill on a tray with a credit-card logo than when the tray has no logo.
(C) In virtually all of the cases in the studies, the patrons who paid bills in cash did not possess credit cards.
(D) In general, restaurant patrons who pay their bills in cash leave larger tips than do those who pay by credit card.
(E) The percentage of restaurant bills paid with a given brand of credit card increases when that credit card’ s logo is displayed on the tray with which the bill is presented.

前面也看了大家很多讨论的帖子，但是发现还是不太清楚
我的理解是：
A(看到信用卡logo)————————>B(tips变多)
但是正确答案的思路是：
否A(看不到信用卡logo)——————>B(tips变少)

但是不是说逆否命题才是正确的吗？
为什么这里要通过双否才能加强题目的结论?

求解啊! 谢谢