The interstitial nucleus, a subregion of the brain's hypothalamus, is

This question is from the June 1999 LSAT (section 3, logical reasoning).

The credited response is E. I hated this question, and hated this answer choices. Narrowed my final selection down to D and E. Both answer choices seemed incredibly weak, leaving me to guess D.

However, after further reflection I realized that, if anything, D seemed to weaken the argument. If disease X affects no more than .05 percent of all male cats, and 1,000 autopsies are performed on male cats who did not contract the disease, finding only 5 of cats with larger interstitial nuclei would seem to support the idea that size affects the likelihood of contracting the disease (because the 995 cats with average sized nuclei did not contract it).

While, in hindsight, E seems slightly more compelling, the answer is so deceptively worded, lending to my frustration in connecting it to the the conclusion of the argument. The stimulus discusses the interstitial nucleus, noting that it is only a subregion of the hypothalamus. E states that the hypothalamus itself is known not to be linked to disease Y, of which X is a subtype. Confusing, but if the interstitial nucleus is a subregion of the hypothalamus I can see how the two could be considered one in the same (a similar argument could be made for the X/Y subtype classification).

An expectedly tricky question # 25.