What is homeostasis?

a. it is a stable external environment that allows survival

c. it is a stable internal environment that allows for survival

b. it is an unstable internal environment

d. it is an unstable external environment that allows for surviva

This seems like it would be a stable internal environment that allows for survival considering homeostasis means the tendency toward a relatively stable equilibrium between interdependent elements. Which this is generally maintained by physiological processes so yeah.