The correct answer is option 2: Homeostasis. Homeostasis refers to the body`s ability to maintain a stable internal environment despite external changes. Sweating during exercise is one of the mechanisms by which the body regulates its temperature and maintains homeostasis.

When we exercise, our muscles generate heat as a byproduct of energy production. To prevent overheating, the body needs to dissipate this excess heat. Sweating is a key mechanism to accomplish this. When we sweat, the moisture on our skin evaporates, which helps to cool down the body. This process of sweating and subsequent evaporation helps regulate body temperature and maintain homeostasis.

The other options in the question are not related to sweating during exercise. Option 1, enthalpy, refers to a thermodynamic quantity related to energy transfer in chemical processes. Option 3, phagocytosis, is the process by which cells engulf and digest particles. Option 4, osmoregulation, is the regulation of water and solute concentration in the body. These options are unrelated to sweating during exercise.

Overall, the correct answer is option 2: Homeostasis, as sweating is a mechanism that helps maintain a stable internal body temperature during exercise.