Can you describe the outer covering of the echinoderm body? (for a starfish)

Their endoskeleton is made of calcareous plaques that, in addition to spines, contain pedicellaria, small pincers used to clean the body and to help capture prey. They also contain a hydrovascular system known as the ambulacral system. Adult echinoderms have pentaradial symmetry; the radial symmetry in these animals is secondary, as it is present only in adults.

Your answer is going to be b.