Question

What is the most likely reason that horses and mountain goats have hooves?
They have homologous structures because they have a common ancestor.
They have analogous structures because they have a common ancestor.
These are vestigial structures in both animals because they are not used.
These are similar structures due genetic mutations.

Answer 1

They have homologous structures because they have a common ancestor.

Hooves in horses and goats are modified keratinized parts of the foot inherited from a common mammalian/ungulate ancestor (divergent evolution yielded single vs. cloven hooves), so the similarity is due to common descent, not independent convergence or vestigial loss.