This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Which of the following is rapid source of energy by resynthesizing ATP for exercising muscles is? 
Select and explain. 
A. Glycolysis, B. Glycogenolysis, C. TCA cycle, D. Phosphocreatine
A: Glycolysis
Answer: A: Glycolysis 
Explanation: Ans: A. Glycolysis(Ref Guyton 13/e p1087. Ganong 25/e p108, 24/e p106)Phosphocreatine:Rapid source of energy by resynthesizing ATP for exercising muscles.During periods of high activity, cycling of phosphorylcreatine allows for quick release of ATP to sustain muscle activity.