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': 'Preganglionic parasympathetic fibers are: \nSelect and explain. \nA. Somatic only, B. Parasympathetic, C. Sympathetic, D. Cholinergic', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]