Answer: Option A
Explanation:
Homeostasis can be defined as the condition in which the body maintains the equilibrium inside the body with respect to the changing environment.
Maintaining the adequate amount of oxygen in the body is also a part of homeostasis.
When the oxygen level in the body goes below normal then the heart rate of the body increases. This supplies more oxygen and the level in the body is maintained.
This condition is an example of homeostasis in the human body.