CRを教えてください（中国問題）

CR（中国問題）を教えてください。
原文
Most major retail electronics chains experienced a dramatic increase in the amount of merchandise lost to shoplifting during the early 1980s. By 1986, however, all large chains had installed new anti-theft devices in their stores. Since this time, there has been a sharp decline in the number of shoplifting incidents taking place in those stores annually.

Which one of the following, if true, would most strengthen the claim that the anti-theft devices were responsible for the decrease in shoplifting?
(A) The average size of electronic merchandise is now small enough to fit into a person's pocket.
(B) The average cost of electronic merchandise decreased since 1986.
(C) Each item in the store was clearly marked with a permanently attached security nubmer
(D) Shoplifting increased at single outlet retail electronics operations since 1986
(E) Shoplifting increased in the retail industry overall since 1986

正解はEだそうですが、だとすると、Dも正解になりうるのではと思います。更に言いますと、Aも正解というような気がします。もっと言いますと、C以外は全て正解と言えると思いますが、皆さんはどう思いますか？宜しくご教示ください。