The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. however, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. which of the following is the most likely explanation for these data?

Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy.                    

Explanation:

Genetic data reveals that the species of humans, bats and whales have evolved from the different  organisms which a common ancestor at early time.  The evolution of upper forelimbs of the humans and the bats have similar skeletal structure  but those oh whales forelimbs skeletal structure has different shapes and proportions.

It is merely because of the adaptation and evolution over time of the whale species who lives in the waters resulted in the adaptation to the aquatic environment and modification of the forelimb skeletal structure.

Thus the answer is ---

Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy.