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': 'Group B muscle fibres are \nSelect and explain. \nA. Sympathetic preganglionic, B. Sympathetic post ganglionic, C. Parasympathetic preganglionic, D. Parasympathetic post ganglionic', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]