Fact 1: Adult echinoderms have radial symmetry.

Fact 2: Animals with radial symmetry lack an anterior and posterior end.

Given the two facts above, answer the question "Which of the following does not have an anterior and posterior end?" with the following options: 
- Adult mammals
 - Adult reptiles
 - Adult birds
 - Adult echinoderms
 - Earth orbiting the Sun
 - an erupting volcano
 - peachleaf willow
 - sensory neurons


 

    Adult echinoderms     