When does heat exhaustion typically occur in an individual?

Heat exhaustion typically occurs when an individual is exposed to high temperatures and loses fluids through sweating. This condition often arises when the body is unable to cool itself down effectively, leading to an imbalance of fluids and electrolytes. During excessive heat exposure, the body sweats to regulate its temperature, and if fluids are not replenished, dehydration can occur. This imbalance can result in symptoms such as heavy sweating, weakness, dizziness, nausea, and even fainting.

While engaging in physical activity without proper hydration and being in confined spaces can contribute to heat-related illnesses, the key factor in heat exhaustion is the exposure to heat coupled with fluid loss. Therefore, option B directly addresses these critical elements of this heat-related condition.