Which of the following is NOT a type of crustacean?

Sea cucumbers are not a type of crustacean; they belong to the phylum Echinodermata, which includes marine animals characterized by their radial symmetry, a water vascular system, and a calcareous endoskeleton. Crustaceans, on the other hand, are classified under the subphylum Crustacea, which includes animals such as crabs, shrimp, and lobsters. These creatures are distinguished by their jointed legs, hard exoskeletons, and segmented bodies. Each of the other options—crabs, shrimp, and lobsters—represents a well-known category of crustaceans, highlighting the diversity within this group and demonstrating the defining characteristics that separate them from sea cucumbers.