The correct answer is: A. A relatively stable internal environment within limits.
Homeostasis is the maintenance of a relatively stable internal environment despite changes in the external environment. This is achieved through a variety of mechanisms, including negative feedback loops, which help to keep the body’s systems in balance.
Option B is incorrect because the body’s internal environment is not constantly changing. In fact, it is very tightly regulated to maintain a relatively stable state.
Option C is incorrect because the body does not always use the lowest possible energy usage. In fact, it often uses more energy than necessary to maintain homeostasis. This is because homeostasis is a priority for the body, and it is willing to expend energy to maintain it.
Option D is incorrect because the body’s internal environment is not static. It is constantly changing, but these changes are kept within limits to maintain homeostasis.