This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Muscle, Subject name: Physiology
A person who is running, the main source of energy he will be using in 1st min is: 
Select and explain. 
A. Glucose, B. Glycogen, C. Fat, D. Phosphagen
B: Glycogen
Answer: B: Glycogen 
Explanation: "The major sources of energy in the 100-m sprint are creatine phosphate (first 4-5 sec) and then anaerobic glycolysis using muscle glycogen as the source of glucose."