请教一道题目！

Manufacturers sometimes discount the price of a product to retailers for a promotion period when the product is advertised to consumers. Such promotion often results in a dramatic increase in amount of product sold by the manufacturers to retailers. Nevertheless, the manufacturers could often make more profit by not holding the promotions.

Which of the following, if true, most strongly supports the claim above about the manufacturers’ profit?
(A) The amount of discount generally offered by manufacturers to retailers is carefully calculated to represent the minimum needed to draw consumers’ attention to the product.
(B) For many consumer products the period of advertising discounted prices to consumers is about a week, not sufficiently long for consumers to become used to the sale price.
(C) For products that are not newly introduced, the purpose of such promotions is to keep the products in the minds of consumers and to attract consumers who are currently using competing products.
(D) During such a promotion retailers tend to accumulate in their warehouses inventory bought at discount; they then sell much of it later at their regular price.
(E) If a manufacturer fails to offer such promotions but its competitor offers them, that competitor will tend to attract consumers away from the manufacturer’s product.

答案是D，D的意思是不是说在促销期间零售商囤积商品，然后等恢复常价后再卖出？那这样的话零售商是可以获得更大利润了，单为什么说supports the claim above about the manufacturers’ profit?有谁能帮我分析下这道题目嘛？谢谢！