Identical twins could not be considered as clones for they are different individuals which came from the same egg and sperm. Clones are produced asexually, a copy of another organism. Even though identical twins share the same DNA, they have different qualities as of the other twin which makes them their own unique self.
Unlike the hippo's ancestor, whale ancestors moved to the sea and evolved into swimming creatures over a period of about 8 million years. Fossils of gigantic ancient whales called Basilosaurus were first mistaken for dinasaur fossils but were later recognised as mammals.
I believe it is either B or A, personally i'm leaning towards B, but at the same time, i don't think that we would be obtaining materials via pollination, so it then causes A to make more sense.
