Answer:
D. Caffeine
Step-by-step explanation:
Ergogenic aids can be termed as nutritional aids, that is mostly used by the Athletes as recovery aid, or potential source of energy which helps to boost or enhance the glycogen level in the body, and helps delay fatigue.
A good example is Caffeine, in which studies have shown that, it helps to enhance mental activities, during most commonly on concentration, alertness, attention etc. It helps to maintain fitness when exhausting and repetitive tasks are involved.