Which of the following does not have an anterior and posterior end?
Options:
- (A) Adult mammals
- (B) Adult reptiles
- (C) Adult birds
- (D) Adult echinoderms
- (E) Earth orbiting the Sun
- (F) an erupting volcano
- (G) peachleaf willow
- (H) sensory neurons Let's solve this problem gradually.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Adult echinoderms have radial symmetry. Animals with radial symmetry lack an anterior and posterior end. Adult echinoderms lack an anterior and posterior end. So the final answer is (D).