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': 'S.A. node acts as a pacemaker of the hea because of the fact that it: \nSelect and explain. \nA. Is capable of generating impulses spontaneously, B. Has rich sympathetic innervations., C. Has poor cholinergic innervations, D. Generates impulses at the highest rate.', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. Generates impulses at the highest rate', 'role': 'assistant'}]