It is on the organ level. The heart consists of cardiac muscle tissue and is part of the cardiovascular organ system. It is basic for the human body to work properly since it provides oxygen for the human body.
Answer: E. A B, and C only
Explanation:
An exoskeleton is a hard, rigid, protective external structure that supports and protects the body of the animal from the damage caused either by injury or by predator. It supports and protects the inner organs and structures, acts as a barrier against desiccation. These act as a point of attachment of the muscles which provides a structural framework to the body. The exoskeleton is waterproof hence, protects the organism from being affected by the external water. It can be seen in the form of shells or scales, nails, hooves and other structures.
