In humans, the appendix is a vestigial structure, small, and is not needed for digestion. In rabbits, the appendix is well developed and is used in the digestion of plant fibers. Which of the following provides the best scientific explanation for the presence of the appendix in both humans and rabbits? A. Rabbits and humans live in environments with similar conditions.

B. Rabbits and humans are both eukaryotes with similar cell structures.

C. The appendix is evolving into a new type of organ in rabbits and humans.

D. The appendix is inherited from a common ancestor of rabbits and humans.