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: Medicine
[{'content': 'Histocompatibility complex associated with narcolepsy - \nSelect and explain. \nA. DR2, B. DR3, C. DR4, D. B4', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]