Biology

The correct answer is C. Nervous System.

The nervous system is the major organ system that includes the brain as its primary organ. The brain is a complex organ responsible for coordinating and controlling many functions of the body, including sensory perception, motor control, cognition, and regulation of bodily systems.

Option A, the circulatory system, consists of the heart, blood vessels, and blood. Its main function is to transport oxygen, nutrients, hormones, and other substances throughout the body. While the brain relies on the circulatory system for oxygen and nutrients, it...