Answer: Foot.
Step-by-step explanation:
Echinoderm means spiny skin. Some example of echinoderms are star fish, sea urchin, sand dollar.
These organisms have no eyes, no brains but they posses tube feet. This feet helps them in respiration, feeding and locomotion.
Tube feet helps in passing food to the oral cavity. This organ performs the similar function to radula in mollusks.