[求助]GWD5-Q31

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 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 given brand of credit card increases when that credit card’s logo is displayed on the tray with which the bill is prepared.

看了以前的讨论，觉得不够明白。

premise：账单有信用卡logo=〉现金结帐tips more。

hypothesis：看到logo=〉提醒超现金支付能力 =〉信用卡持有者spend more

question：加强研究解释。

这里存在两个问题：

一、tips more不等于spend more。小费和花费应该两个概念。

二、即使承认二者等价，有能力=〉spend more，怎么能通过：有义务=〉spend less加强？ 这里不存在逆否关系呀？

请指教！