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 __________.
(A) 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
Conclusion says that shopping at ShopperKing is not necessarily expensive. Notice that the premise said that the "total" was 5 percent higher in comparison of SK (ShopperKing) and FK(FoodBasket) supermarkets. However, we do not know any individual prices of each item in these two stores.
For example, a kid is going to the store with his mom. Prices are as follows:
Itesm/ SK niu FK
Toysnu 2 ndiuc 4
Food n40 ddd 30
Total c 42 ncc 34
From this table, we see that: overall, the kid and the mom would spend more if shopping at SK than at FK. However, If the kid buys toys regularly, he would spend less at SK and more at FK. Therefore, shopping at SK is not necessarily expensive.
(B) for shoppers with more than 20 items, the ShopperKing totals averaged more than five percent higher than the FoodBasket totals
Conclusion says that shopping at ShopperKing is not necessarily expensive. However, B confirms further that it is more expensive to shop at ShopperKing. Weakens the argument. Wrong.
(C) many shoppers consider factors other than price in choosing the supermarket at which they shop most regularly
The conclusion talks about the comparison of prices. C talks about how to choose supermarket. Irrelevant! No matter how C will tell you the decision of choosing, it still cannot explain shopping at which supermarket is cheaper. For example, a shopper values quality the most. SK has higher better quality and higher price, so the shopper would shop at SK for higher quality. However, that doesn't explain anything about shopping at SK might not be necessarily expensive (which is the conclusion).