Question

the forearms of humans and horses are used for different things, but their bone structure is very similar. these can be called select vestigial structures. derived characteristics. homologous structures.

Explanation:

These structures share a similar underlying bone structure despite having different functions (human forearm for grasping, horse forearm for locomotion), which is the defining trait of this type of anatomical structure. Vestigial structures are reduced and non-functional, derived characteristics are new traits in a lineage, and analogous structures have similar functions but different origins.

Answer:

homologous structures.