Shells are the exoskeletons of clams, snails and oysters. Hope that helps
Endotherms, such as birds and mammals, use metabolic heat to maintain a stable internal temperature, often one different from the environment. Ectotherms, like lizards and snakes, do not use metabolic heat to maintain their body temperature but take on the temperature of the environment.
Answer: The answer is C.
C. They're examples of cell organelles.
Explanation: I just looked up the question and I got that answer.
