Answer:
D. horses
Explanation:
The medieval-era was not a fan of pets. If they even keep one, it was because of the animal's functional reasons. In addition to this, the church wasn't in favor of animal's having souls.
The animals being extensively studied during this time were the horses and the cattle. The health of these animals were very important for they served important purposes in the life of people. They were used for transportation, sources of food and for war reasons.
These animals were extensively studied only because of their use and not because of health reasons alone.
