问GWD-12-Q40

Which of the following most logically completes the argument?

Researchers recently asked dozens of shoppers, chosen at random coming out of a FoodBasket supermarket, what they had purchased.  The prices of the very same items at the nearest ShopperKing supermarket were totaled and compared with the FoodBasket total.  The ShopperKing totals averaged five percent higher than the FoodBasket totals.  Nevertheless, this result does not necessarily show that shoppers at ShopperKing would save money overall by shopping at FoodBasket instead, since ______.

1. shoppers who shop regularly at a given supermarket generally choose that store for the low prices offered on the items that they purchase most often

2. for shoppers with more than 20 items, the ShopperKing totals averaged more than five percent higher than the FoodBasket totals

3. many shoppers consider factors other than price in choosing the supermarket at which they shop most regularly

4. there is little variation from month to month in the overall quantity of purchases made at supermarkets by a given shopper

5. none of the people who conducted the research were employees of the FoodBasket supermarket

答案选a, 我选了b，他说超过20件总的价格才超过5%，但假如不超过20件，不就不超过5%了，不就是没怎么便宜了吗？请NN解释下~~

A经常买的东西的价格高低决定了购买者对超市的选择，而不是随机选取的货物价格对比。

B购买件数和选择无关，超过20件sk贵不能推出少于20件贵或便宜