Answer:
Option B and option C are correct.
Explanation:
Endoskeleton - An internal support structure or skeleton is on the inside of a body, composed of calcium or mineralized tissue.
B. Bones in mammals - are endoskeleton, it supports the body in its shape.
C. Calcium-rich plates in echinoderms are acts like exoskeletons but most of the cases a thin tissue surround skeleton so it is an endoskeleton.
