Which of the following best classifies an ergogenic aid?

• A. A training program or diet plan exclusively designed by a coach to increase endurance without use of supplements or equipment
• B. Any nutrient that is essential for life regardless of its use for performance, such as vitamins and minerals required for normal physiology and not specifically targeted to enhance performance
• C. Only pharmacological agents that are banned in sport and increase muscle mass beyond natural limits through hormonal manipulation
• D. A substance, device, or technique used to enhance athletic performance or recovery

Answer: (D)