This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': "Heteopic calcification occurs in \nSelect and explain. \nA. Ankylosing spondylitis, B. Rieter's syndrome, C. Forrestier'disease, D. Rheumatic ahritis", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ref, Robbins 7/e p41-2; Harrison 17/e p1952', 'role': 'assistant'}]