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': 'Cardiac muscles action potential at plateau is due to \nSelect and explain. \nA. Influx of Na, B. Efflux of K, C. Influx of ca, D. Influx of cl', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ca2+ influx through more slowly opening Ca2+ channels (the Ca2+ current, ICA) produces the plateau phaseRepolarization is due to net K+ efflux through multiple types of K+ channelsThe initial depolarization is due to Na+ influx through rapidly opening Na+ channels Ref: Ganong's Review of Medical Physiology Twenty-Third Edition pg:491", 'role': 'assistant'}]