Which process allows organisms to keep internal conditions relatively constant despite changes in external conditions?

homeostasis

hibernation

hypothermia

Homeostasis

Explanation:

Walter Cannon elaborated the concept of homeostasis from the investigations

carried out by Claude Bernard, creator of Experimental Medicine.

The concept of homeostasis, as Cannon formulated it in his capital work,  the Wisdom of the Body implies a dynamic equilibrium, maintained interactively by the constant dialectic between internal kinetics and  variations of the external environment. Homeostatic regulation is set to different  levels, from molecular-subcellular to suprapersonal or social, through the  global consideration of the individual as a whole . The study of isolated aspects of this systematic organization must give us, for  strength, a partial vision. Human functioning is always influenced by a  hierarchically organized activity of suprasystems and related subsystems.

that is wrong, its not thymus.