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: Surgery
[{'content': 'Absolute indication for surgery in hyperparathyroidism is \nSelect and explain. \nA. Serum calcium < 2.85mmol/lit, B. Increased bone density, C. Urinary tract calculi, D. Patient more than 50 years of age', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]