Which statement best defines homeostasis?

• A. The movement of blood through vessels
• B. The breakdown of fats for energy
• C. The regulation of body temperature during exercise
• D. The maintenance of stable internal conditions

Answer: (D)

Homeostasis is the maintenance of stable internal conditions. The body keeps variables like temperature, pH, fluid and electrolyte balance, and energy supply within narrow ranges despite changes in the external environment. This relies on feedback systems that sense deviations and adjust processes to restore balance.

Regulating body temperature during exercise is an example of homeostasis in action, but it’s a specific instance of the broader concept. Movement of blood through vessels describes circulation, which supports homeostasis but isn’t the definition. The breakdown of fats for energy describes metabolism, not the regulatory idea itself.