Critical Reasoning

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 creditcard
logo. Consumer psychologists hypothesize that
simply seeing a credit-card logo makes many creditcard
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 fi nancial 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.

OA is (B)

What's wrong with (A)?