24.The interstitial nucleus, a sub-region of the brain’s hypothalamus, is typically smaller for male cats than for female cats. A neurobiologist performed autopsies on male cats who died from disease X, a disease affecting no more than .05 percent of male cats, and found that these male cats had interstitial nuclei that were as large as those generally found in female cats. Thus, the size of the interstitial nucleus determines whether or not male cats can contract disease X.

Which one of the following statements, if true, most seriously weakens the argument?

A. No female cats have been known to contract disease X, which is a subtype of disease Y. B. Many male cats that contract disease X also contract disease Z, the cause of which is unknown. C. the interstitial nuclei of female cats who contact disease X are larger than those of female cats who do not contract disease X. D. Of 1,000 autopsies on male cats that did not contract disease X, 5 revealed interstitial nuclei larger than those of the average male cat. E. The hypothalamus is known not to be causally linked to disease Y, and disease X is a subtype of disease Y.

E is the best answer. Disease X is the subtype is disease Y, if disease Y has no link with hypothalamus, X must have no link with hypothalamus. A, C talked about the female cat, that can't weaken the argument. B talked about another disease Z, doesn't weaken the argument. D just shows some data, which cannot weaken the argument.

E选项的意思是hpothalamus与x无关，削弱原文从hypothalamus的大小来判断是否的了x。 但是原文并没有提到专家检查了多少只猫才发现得过x，hypothalamus就大，那我们是不是可以认为这种联系是没有例外的？那这样E选项否定了这个前提？削弱可以否定前提吗？

看一下D。1000只没有病的猫，5只猫的hypothalamus比正常的大，因为1000在概率论里足以构成一个大样本，所以可推出：在没有得病的猫里，hypothalamus大的概率在0.5%，说明即使没得病，也有0.5%左右的猫会有大的hypothalamus，而原题目中说得x病的概率低于0.05%。前者的概率是后者的10倍左右。这是不是削弱？