我觉得22题的答案不对，找到了GWD的原题和讲解
22.【加油站刺激生意】by 牛与鸡 （710 Q51 V34）
一个加油站为了刺激salesman 有一个promotion，就是加油达到多少多少gallon就可以免费洗车，sales果然比去年同期增加了，因此promotion有效。
问evaluate
狗主选的是如果没有promotion的话那些达到某gallon的顾客是否加油的量会少但是次数会多
这道题应该是GWD原题，Q17:GWD32-Q8
Last August the XT chain of gasoline stations had a temporary sales promotion in effect. In the promotion, any customer who made a purchase of ten or more gallons of gasoline was entitled to a free car wash. For the month of August, XT experienced a ten percent increase in gasoline sales as compared to sales in August the previous year, so evidently the promotion was successful as a means of boosting sales.
In evaluating the argument, it would be most helpful to answer which of the following?
A. In the areas in which XT’s gasoline stations operate, how did total combined gasoline sales for all gasoline stations last August compare with sales for the previous August?
B. Was the money that XT earned from the increase in gasoline sales enough to offset the cost of providing free car washes during the promotion?
C. Were there any customers who bought ten or more gallons at an XT gasoline station during the promotion who would have or more gallons at an XT gasoline in lower quantities, but more frequently, if the promotion had not been in effect?
D. Did XT or any of its gasoline stations have to pay other businesses to provide the car washes that customers were offered in the promotion?
E. Are XT’s gasoline sales in August usually significantly higher than one twelfth of XT’s annual gasoline sales?
正确答案应该是A
关于为什么选A的原因：
文中的结论是promotion是boosting sales的一种有效手段
C中的总revenue是不变的，所以并没有说明promotion带来的效果
但是A的意思是
看看整个区域的加油站的last August和Previous August的销量比较，
如果整个区域的销量有提高的，就对结论weaken了，因为你不知道到底是不是promotion带来的sales增长，有可能是外部经济（如油价下降）的影响
反之，对结论是支持作用，说明更加有可能是promotion使得sales的增长
-- by 会员 haoge1937 (2011/5/11 12:26:18)
3Q~