Echinoderms have a unique water vascular system with tube feet, and echinoderms have a hydraulic system of locomotion called the water vascular system. Given these facts, how do echinoderms use their feet to locomote themselves among the following options:
- one at a time
 - to move people
 - running and lifting
 - protein channels
 - a hydraulic system
 - it needs them
 - undulations
 - It helps them survive


 

     a hydraulic system    