Homeostasis refers to:

Homeostasis is a fundamental concept in physiology that refers to the body's ability to maintain a stable internal environment despite external changes. The correct understanding aligns with the role of the kidneys, which are pivotal in regulating factors such as electrolyte levels, fluid balance, and the acid-base status of the blood. By filtering waste and excess substances from the bloodstream, the kidneys help ensure that the body's chemical balance remains consistent, which is crucial for optimal cellular function and overall health.

While the body's response to temperature changes, heart rhythm regulation, and liver detoxification are all important physiological processes, they are specific aspects of homeostasis rather than a comprehensive definition. The kidneys' function demonstrates a clear mechanism through which homeostasis is actively maintained in the body.