Which of the following is a method to prevent heat-related illnesses?

Staying hydrated is crucial for preventing heat-related illnesses. When the body experiences heat, it relies on sweat to cool itself, and hydration is essential for this process. Adequate fluid intake helps maintain blood volume and allows for effective thermoregulation. Dehydration can impair the body's ability to cool itself, leading to heat exhaustion or heat stroke, conditions that arise when the body overheats.

While regular meal breaks can contribute to overall well-being and provide energy, they do not directly address the body's temperature regulation in warm conditions. Dressing in layers is more appropriate for cold environments, as it can trap heat. Avoiding all physical activity, on the other hand, is impractical and not necessary for preventing heat-related illnesses, as appropriate activity with measures like hydration can be safe and beneficial. Thus, staying hydrated stands out as the most effective method for mitigating heat-related risks.