This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
[{'content': 'Postganglionic sympathetic fibres are \nSelect and explain. \nA. A alpha, B. C, C. B fibres, D. A gamma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The axons of postganglionic neurons are mostly unmyelinated C fibres and terminate on visceral effectors. Ref: Ganong&;s review of medical physiology; 23rd edition; pg:263.', 'role': 'assistant'}]