This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Absolute refractory period is due to: 
Select and explain. 
A. Opening of calcium channels, B. Opening of potassium channals, C. Closure of Active gates of sodium channals, D. Closure of inactive gates of sodium channals
D: Closure of inactive gates of sodium channals
Answer: D: Closure of inactive gates of sodium channals 
Explanation: Inactivated gates of sodium are closed during depolarization and Remain closed until repolarization no action potential can occure untill inactivated sodium gate are opened Ref:Guyton and Hall textbook of medical physiology 12th edition,page number:70