24. The interstitial nucleus, a subregion 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 who 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 who 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.

答案是 E，但 X 与Y 无关呀？

 subtype: 比如动物分为warm-blooded and cold-blooded(这里如果定义为type), 那么subtype指warm-blooded下的分支，如猫科动物是warm-blooded的subtype.

再比如：Shanghai Branch of Bank-of-China中国银行上海分行，Waitan subbrance则为外滩支行