Question

what are echinoderms known for?
being able to fly
being able to regenerate body parts
being able to eat any food

Explanation:

Echinoderms (e.g., starfish) are marine invertebrates known for their ability to regenerate lost body parts, such as arms. Flying is not a trait of echinoderms, and they do not eat any food (they have specific diets). Thus, regeneration is their key known feature.

Answer:

being able to regenerate body parts