Fact 1: Echinoderms lack a centralized nervous system.

Fact 2: All echinoderms are deuterostomes .

Given the two facts above, answer the question "Some deuterostomes lack a centralized what?" with the following options: 
- DNA
 - eardrum
 - critical organs
 - permineralization
 - A ruler
 - nervous system
 - communication center
 - respiratory system


 

      nervous system   