This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Conducting System of Hea, Subject name: Physiology
[{'content': 'Most rapidly depolarizing fibers in the ventricle are: \nSelect and explain. \nA. Fibers at the apex, B. Fibers in the middle of the ventricle, C. Fibers at the base, D. All fibers from apex to base (depolarize equally rapidly)', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Purkinje fibers and ventricular fibers are basically rapidly depolarizing fibers. Yet, the rates of their depolarization are different. Fiber at the apex depolarizes relatively slow. As one moves toward base, the rates of depolarization become more and more rapid. Fiber at the base depolarizes most rapidly. It immediately repolarizes as well.Then, the repolarization spreads in the reverse direction. When repolarization reaches the apex, the apical fiber has just now finished its depolarization; it now begins to repolarize.', 'role': 'assistant'}]