The right answer is 2) the maintenance of homeostasis.
Homeostasis is a physiological process that allows certain constants of the internal environment of the body (all the body fluids) necessary for its proper functioning (between the limits of normal values) to be maintained.
For example :
*Temperature.
* The functioning of the heart and vessels.
* The concentration of blood, lymph and cerebrospinal fluid (fluid contained in the cerebral ventricles, and in the ependymal canal which is in the center of the spinal cord).
*Blood pressure.
The whole regulation of homeostasis is through the autonomic nervous system (autonomic nervous system) and endocrine (hormonal) glands.