Concept:The pentadactyl limb shows a shared basic five-bone structure in different animals.
This similarity points to a common ancestor.
Explanation:Frogs, birds, horses, whales, and humans use their forelimbs for different purposes.
However, all these limbs contain the same five-digit bone pattern.
Such structural similarity is called homology.
Homologous structures are best explained by common descent.
Therefore, the pentadactyl plan is a proof of evolution.
Answer:B. evolution