OG 16 verbal

小仙女rachel

Colorless diamonds can command high prices as gemstones. A type of less valuable diamonds can be treated to remove all color. Only sophisticated tests can distinguish such treated diamonds from naturally colorless ones. However, only 2 percent of diamonds mined are of the colored type that can be successfully treated, and many of those are of insufficient quality to make the treatment worthwhile. Surely, therefore, the vast majority of colorless diamonds sold by jewelers are naturally colorless.
A serious flaw in the reasoning of the argument is that
(A) comparisons between the price diamonds command as gemstones and their value for other uses are omitted
(B) information about the rarity of treated diamonds is not combined with information about the rarity of naturally colorless, gemstone diamonds
(C) the possibility that colored diamonds might be used as gemstones, even without having been treated, is ignored
(D) the currently available method for making colorless diamonds from colored ones is treated as though it were the only possible method for doing so
(E) the difficulty that a customer of a jeweler would have in distinguishing a naturally colorless diamond from a treated one is not taken into account

麻烦问一下各路大神，这个题的D选项为什么不对。
我的理解是：现在的这种方法是唯一方法。这样会变成原文的一个gap/flaw啊，因为原文说，2%的diamonds mined can be successfully treated，那么如果不认为这种方法是唯一方法的话，产量就会多，就攻击了原文的结论啊。

谢谢！！！！
答案对D是这样解释的：The argument only concerns the types of colorless diamonds sold now, not the types that may be sold in the future if other treatment methods are discovered.
我没太搞清楚。。。

小仙女rachel

期待回复