Final answer:
In physical activity lasting less than one hour, water is the most appropriate fluid replacement.
Step-by-step explanation:
In physical activity lasting less than one hour, the most appropriate fluid replacement is water.
For activities lasting less than one hour, such as low-intensity or skill-based exercises, water is sufficient to replace the fluids lost through sweat and prevent dehydration. Sports drinks, which contain electrolytes and carbohydrates, are designed for longer duration and higher intensity activities where there is a greater need for replenishing electrolytes and energy stores.
It is important to note that individual fluid needs may vary based on factors such as body weight, intensity of exercise, and environmental conditions. Hydration should be personalized based on these factors.