What aspect of Gulliver's appearance do the Houyhnhnms admire?

The Houyhnhnms admire the softness of Gulliver's skin primarily because they are a species of intelligent horses who have a very different perception of what constitutes beauty and attractiveness. In their society, their own skin is covered in hair and they prioritize qualities such as smoothness and softness, which they find appealing in Gulliver's human form. This admiration highlights the contrast between human beings and the Houyhnhnms, as they are not only fascinated by his physical attributes but also reflect their values and standards of beauty. This moment serves to showcase their civilized and reasoned nature, as they approach the evaluation of Gulliver not with judgment or prejudice, but with a genuine appreciation for what they observe. The other choices, such as eye color, clothing style, and hair length, do not hold the same significance within the context of the Houyhnhnms' perspective. Their appreciation for Gulliver’s skin exemplifies a key theme in "Gulliver's Travels" regarding differing cultural standards and the nature of beauty as perceived by various societies.