Answer:
A) vestigial
Step-by-step explanation:
Vestigial structure is an atrophied organ present in some living organisms that has no function for a very limited function, but has a great function in the body of another animal. This structure is the result of the evolution of species and serves as evidence of the existence of common ancestors between two animals that are not biologically similar. An example of this can be seen in the question above, which shows that whales have useless leg bones that float within their bodies and that serve as evidence to claim that whales have evolved from terrestrial animals similar to large otters