[求助]在OG和大全中没找到对应题，陈向东P182第52题，请NN们不要不理我

As a promotion experiment, Omega Company distributed four million catalogs. In one of the two versions of the catalog, the description of each item for sale mentioned a "Made by Hand" label. The number of purchases from consumers receiving that catalog was twenty percent greater than the number of purchases from consumers receiving a catalog that did not mention the label. Thus, the mention of the label stimulated sales.

Which of the following, if true, could best be used to challenge the conclusion drawn above?

A. Consumers receiving the catalog mentioning the label had previously purschased items from Omega Company by mail but consumers receiving the other catalog had not.

D. Omega Company mailed three times as many catalogs that did not mention the "Made by Hand " label as catalogs that did mention the label.

答案是A. 我理解为什么A是对的，但同时觉得D也没问题。请各位NN释疑。谢谢！

题目结论说标签刺激销售.答案A强调以前的购买经验.答案D说有标签的目录是没有标签的目录的3倍,貌似是支持结论,而且这个3倍和题目里的20%也没什么联系.

我觉得要相信自己的思路和感觉,找到对的就别管其他的了.

不是，我就是因为当时做题的时候没有自己的思路，徘徊在AD之间不知道选谁好。

D的话，我当时是这样想的：1，D说明除了有无标签外还有其他的原因发送量在影响购买量；

2，有手工制造标签的catalog数量比没有的多三倍，而销售量只增加了20%。这样一来，即使是有标签和没标签的促销效果一样的话，有标签的销售量都应该是没标签的300%，更不用说结论中的有标签的比没标签的促销效果好了（这样的话应该大于300%才对啊？），而现在却只有20%，那么说明有标签根本没有理想中的促销效果。

不知道我这样想的问题在哪里，请NN们帮我指正！