Answer:
"The limb bones are similar across these species because they share a common ancestor is a right option.
Step-by-step explanation:
Forelimb (humerus, ulna, and radius) is a homologous structure in all vertebrates. This means that these structures are evolved from the same lineage. Homologous organs could perform different functions but they are structurally similar.
If there is any similarity in different animal's forelimb structure (e.g. horses, goats, and mice), then they are considered to be of same evolutionary origin. Their structures are similar but not function. Evolutionary biology tells us that homologous structures are adapted to different environments as a result of modifications from a common ancestor.
In a nutshell, forelimbs of ancestral vertebrates have evolved into the running forelegs of mice, goats and horses, and the grasping hands of humans.