Which of the following describe(s) echinoderms?
a. They have an exoskeleton of hard calcareous plates.
b. Tubefeet provide motility in most species.
c. Digestion occurs completely outside of the organism.
d. Hemolymph circulates in the water vascular system.
e. They are found in both freshwater and saltwater environments.
Answer: b. Tubefeet provide motility in most species.