Echinoderms lack a centralized nervous system, and echinoderms include starfish, sea urchins, and sea cucumbers. Given these facts, starfish, sea urchins and sea cucumbers lack a what among the following options:
- characteristics
 - the body's largest organ
 - watery habitat
 - centralized nervous system
 - functioning arm
 - underwater life
 - biological diversity
 - epidermis and dermis


 

    centralized nervous system     