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: Pathology
[{'content': 'Thromboangitis obliterans is associated with \nSelect and explain. \nA. HLA - DR4, B. HLA - DR2, C. HLA - B5, D. HLA - B27', 'role': 'user'}, {'content': 'Answer: C \nExplanation: HLA A9 and HLA B5 is associated with increased risk of Thromboangitis obliterans (TAO) HLA-B12 is protective against TAO.', 'role': 'assistant'}]