Mare is to horse as ewe is to what?

The correct answer is sheep because a mare is a female horse, while a ewe is a female sheep. This relationship highlights the pattern of identifying gender-specific terms for these animals. In both instances, the terms describe the female of a species.

The other options do not maintain this specific gender association within the same species. A lioness refers to a female lion, a goat pertains to a different animal entirely, and a doe typically refers to a female deer, creating alternative relationships that do not follow the same pattern as the mare and horse. Therefore, sheep correctly completes the analogy based on gender specificity within the same animal category.