Which term describes the skeletons of sharks and rays composed primarily of cartilage?

• A. Chitin
• B. Chondrichthyes
• C. Crustacea
• D. Cetacea

Answer: (B)

Sharks and rays have skeletons made mostly of cartilage, a lighter and more flexible connective tissue. This trait defines them as cartilaginous fish, classified in the class Chondrichthyes. Cartilage supports the body without heavy bone and contributes to their buoyancy and maneuverability in the open water. The other terms refer to different things: chitin is the tough carbohydrate used in some arthropod exoskeletons, crustacea is a group of crustaceans, and cetacea includes whales and dolphins. So the term that describes the skeletons of sharks and rays is Chondrichthyes.