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': 'Crystals deposited in Pseudogout: March 2013 (d) \nSelect and explain. \nA. Sodium biurate, B. Calcium oxalate, C. Sodium pyrophosphate, D. Amyloid', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C i.e. Sodium pyrophosphate', 'role': 'assistant'}]