Fact 1: Echinoderms use pheromones to communicate with each other.

Fact 2: Another group of echinoderms are the echinoids.

Given the two facts above, answer the question "what do echinoids use to communicate?" with the following options: 
- light
 - Chemical energy
 - Decibels
 - pheremones
 - writing
 - Energy
 - heat produced
 - language


 

    pheremones     