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': 'Pain is conducted by: \nSelect and explain. \nA. A-alpha fibers, B. A-beta fibers, C. A-gamma fibers, D. A-delta fibers', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]