In a particular experiment on shopper behavior, two aisles in a retail store were painted differently. One aisle was painted with bright colors whereas the other was painted in uniform black and gray. Over a three month period, it was noticed that sales from the aisle painted in bright and cheerful colors were nearly twice those from the aisle painted in black and gray. This study shows that the use of color has a significant impact on shoppers' purchasing behavior.

Which of the following, if true, would most strengthen the conclusion drawn in the experiment above?

A) The aisle painted in bright colors contained only store brands; the aisle painted in black and gray contained premium brands.
B) The two aisles were selected because they had similar location, pricing, and product selection.
C) The differing inventories of the two aisles both contained a mix of market-leader and store-brand items
D) The brightly colored aisle was painted in the same colors that the store had historically used for its discount coupons and flyers
E) The brightly colored aisle was located closer to the store's entrance

Conclusion: Color has significant impact on purchasing behavior
Premise: brightly colored aisle had twice as many sales as aisle painted black and gray

This is a causality argument. The claim is that it's the color that's responsible for the sales differential. As an arrow diagram, it might look like this:
brightly colored aisles ---> more sales

The question: was it really the bright colors that sparked the increase in sales? Could it have been something else? Couldn't the brightly colored aisle have had more popular products or better prices, etc? So we want an answer choice that is going to strengthen the notion that it wasn't something else responsible for the higher sales in the brightly colored aisle. This is what B does.

D is a weakener. If the colors in this particular store are linked in the minds of shoppers with discounts, then it could be the lure of saving money that's prompting the increase in sales, not the colors themselves. Put another way, if D were true, we couldn't claim that bright colors lead shoppers to purchase more in general. If you owned a rival store, and bright colors weren't linked to discounts at your store, you couldn't conclude that brightening the colors of your aisles would boost sales.