The correct option is D Convergent evolution
Convergent evolution describes the independent evolution of similar features in species of different lineages. Both sharks and whales, seals have similar body forms, yet are only distantly related: sharks are fish and whales, seals are mammals. Such similarities are a result of them being exposed to the same selective pressures. Within these organisms, changes that aid in swimming has been favored. Thus, over time, they developed similar appearances (morphology), even though they are not closely related. So these species came to the same function, swimming, but did so separately from each other. They have "converged" on this useful trait.