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': 'SA node acts as a pacemaker of the heart 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: SA node acts as the pacemaker of heart because the impulses generated here is having the fastest rate.', 'role': 'assistant'}]