Homeostasis is best defined as a a feedback system that prevents a body system from changing; b a feedback system designed to maintain body systems within an optimal range while responding to environmental or external change; c a positive feedback control that enables the body to respond to changes in the external environment by changing the internal environment; d a control system designed to regulate the external environment by making subtle changes to the internal environment; e a control system that causes body systems to change if the external environment remains constant