A group of organs that work together to perform major functions.

• A. Organ
• B. Tissue
• C. Organ System
• D. Gland

Answer: (C)

This question tests how the body is organized in hierarchical levels of collaboration. A tissue is a group of similar cells doing a common job, and an organ is made of different tissues working together to perform a specific task, like the heart pumping blood. A gland is a type of organ focused on secretion. An organ system, however, is a group of two or more organs that cooperate to carry out a major function needed by the organism, such as digestion, circulation, or respiration. The phrase “group of organs that work together to perform major functions” directly describes an organ system, because it emphasizes the coordination of multiple organs to achieve a broad physiological purpose. For example, the circulatory system combines the heart, blood vessels, and blood to move nutrients and oxygen through the body, while the digestive system includes the stomach, intestines, and associated organs to break down and absorb nutrients.