Answer: The correct answer would be option a.
Step-by-step explanation:
There are three main energy systems in human body.
1. ATP-CP: ATP-creatine phosphate system is used for initial 4-5 seconds.
2. Anaerobic: During high intensity short duration activity this system is used in which glycolysis and fermentation helps in production of energy.
3. Aerobic: It is active during long duration low intensity exercises such as marathon. In this system, glycolysis, utilization of all stored glycogen, and lipolysis take place.
Once most of the glycogen stores are depleted body starts breaking down stored fats for energy production.
Thus, the correct answer would be option a.