This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'Plateau phase of ventricular muscle is d/t opening of \nSelect and explain. \nA. Na+ channel, B. K+ channel, C. Ca - Na channel, D. Closure of K+ channel', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ca2+ influx through more slowly opening Ca2+ channels produces the plateau phaseThe initial depolarization is due to Na+ influx through rapidly opening Na+ channels Repolarization is due to net K+ efflux through multiple types of K+ channels', 'role': 'assistant'}]