Q9: Studies in restaurants show that the tips left by customers who pay their bill in cash tend to be largerwhen 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.

答案是B，请问为什么呢？我认为B明显是削弱阿，因为题干说在任何条件下A=>B,但B选项说在用户拮据的情况下A=>B反。这样就用反例来证明题干的论断不正确了

IMHO, the stem focus on the relationship between the "credit card logo" and "a person's tipping behavior".

B means when you see the credit card logo, it will reminds you that you still have debt to pay, so you won't tip much. The logo influenced your tipping behavior, so support the point.