ANSWER:
To regulate homeostasis in the hiker, the process of hydration is used.
Step-by-step explanation:
This is because the body of the hiker is overwhelmed with heat and water which can help the hiker to keep his body and cells hydrated.
Hydration basically involves intake of water so that the body can survive. Every cell and tissue of the body needs water to function and hydrating helps the hiker to hydrate the cells. This in turn will help the hiker to lower and maintain the body temperature which will bring relief.