This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immune system, Subject name: Medicine
[{'content': 'Ankylosing spondylitis may be associated with \nSelect and explain. \nA. Atrial fibrillation, B. Pulmonary stenosis, C. Aoic incompetence, D. Mitral stenosis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ref Davidson 23e p1030', 'role': 'assistant'}]