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
[{'content': 'The absolute refractory period of an action potential is due to: \nSelect and explain. \nA. Insufficient neurotransmitter, B. Depletion of intracellular Na+, C. Inactivation of Na+ K+ ATPase, D. Voltage inactivation of the Na+ channel', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]