What do echinoderms have instead of brains?

Instead of a brain, echinoderms have a ring of nerves located around their mouth area that governs their nervous responses. This ring coordinates their motion, their eating, basically anything that requires nerve control.

Explanation:

the atmospheric gas that forms a mild acid when dissolved in water is called carbon dioxide. the correct answer is a. 2.) chemical weathering would cause an inscription on a marble headstone to become harder and harder to read over time.