Turtles are classified in the order Testudines. Some turtles are aquatic and others are terrestrial. Aquatic turtles have webbed feet and short claws, but terrestrial turtles do not. Which of the following statements best explains why aquatic turtles and terrestrial turtles are classified in the same order but have such different feet?
A. Aquatic turtles evolved from fish, and terrestrial turtles evolved from reptiles.
B. Aquatic turtles and terrestrial turtles have similar body plans, but they grow at different rates.
C. Aquatic turtles interbred with different species, and terrestrial turtles bred only within their own species.
D. Aquatic turtles and terrestrial turtles evolved from a common ancestor, but they have adapted to different environments.