Final answer:
The correct option for fluid/electrolyte intake during high-intensity events of 1-3 hours is 500-1,000 ml of water with NaCl and 6-8% carbohydrate per hour, which aligns with guidelines for sodium content in sports drinks.
Step-by-step explanation:
The recommended fluid/electrolyte intake during high-intensity events of one to three hours is 500-1,000 ml water with NaCl and 6-8% carbohydrate/hour. This recommendation is consistent with guidelines suggesting that a sports drink should contain adequate levels of sodium, such as 125 milligrams of sodium per 8 ounces, to help replenish sodium lost in sweat and promote fluid uptake, which in turn improves hydration. These beverages are designed to replace electrolytes, such as sodium and potassium, and carbohydrates that are lost through sweat during intense exercise.