The correct option is <u>C. The nervous system when the brain regulates the body's breathing and heart rate.</u>
Explanation:
The main function of the respiratory system is to exchange oxygen for carbon dioxide in the body.
The brain controls the rate at which the heart pumps blood. The pumping of the heart supplies oxygenated blood to other parts of the body. Hence, the rate at which heart pumps blood is very important to maintain homeostasis of the respiratory system.
The brain regulates the rate at which a person breathes. This rate is very important to breathe in the right amount of oxygen and to breathe out the right amount of carbon dioxide.
The answer is the third option! Photosynthesis is the process in which plants convert carbon dioxide, water, and light energy into oxygen and glucose! Have a great day, I hope this helped! ^_^