Which best defines homeostasis?

1. modifying the external environment

2. maintaining a stable internal environment

3. controlling what enters and exits the cell

4. movement of materials into the cell

B. maintaining a stable internal environment

The answer is (2) maintaining a stable internal environment.

Homeostasis is the process by which an organism tries to stabilise the internal body metabolism in response to external disturbances or changes. Example, when a person goes out into the snow, his body process will get overwhelmed by the sudden drop in the temperature. The body will try to stabilise its internal temperature by producing more heat in response to the cold exterior.