This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Excitation and Action Potiential, Subject name: Physiology
[{'content': 'Long acting calcium channel act in which pa of action potential? \nSelect and explain. \nA. 0, B. 1, C. 2, D. 3', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Phases Characteristics 0 (depolarization) Opening of fast Na channels. 1 (initial repolarization) Closure of fast Na channels & K+ efflux through open K+ channels. 2 (plateau) L - type slow Ca++ channels open & fast K+ channels close. 3 (rapid repolarization) Ca++ channels close & slow K+ channel open. 4 (resting membrane potential) Average around - 90 mv.', 'role': 'assistant'}]