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题库 / OG2017V-CR-167
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
comparisons between the price diamonds command as gemstones and their value for other uses are omitted
information about the rarity of treated diamonds is not combined with information about the rarity of naturally colorless, gemstone diamonds
the possibility that colored diamonds might be used as gemstones, even without having been treated, is ignored
the currently available method for making colorless diamonds from colored ones is treated as though it were the only possible method for doing so
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
command high prices /as gemstones——作为G要价很高
only 2 percent of diamonds mined钻石矿里只有2%是假冒钻石
注意：1.分母是所有钻石矿
2.有分数，注意考虑相对量和绝对量
P：假冒钻石只占总钻石的2%（比例小）
C：大部分无色钻石都是真的
Gap：可能真无色的比例也很小，也许远＜2%，那么大部分钻石反而是加的
所以gap在于，没有比较 假冒钻石和 真无色钻石的数量
因为2%的分母是所有钻石，而不是无色钻石
感谢
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