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: Medicine
[{'content': 'Which of the following is most appropriate cause of urinary stone formation? \nSelect and explain. \nA. High urinary oxalate, B. Low urinary Mg, C. Low urinary sodium, D. High urinary chloride', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]