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': 'Commonest stone in case of UTI - \nSelect and explain. \nA. Phosphate, B. Urate, C. Cysteine, D. Calcium oxalate', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans is 'a' ie Phosphate Phosphate or struvite stones are infection stones associated with urea splitting organisms i.e. Proteus, Pseudomonas, Providincia, Klebsiella, Staphylococci and Mycoplasma. The high ammonium concentration desired from urea-splitting organisms results in an alkaline urinary pH, reauired for the precipitation of phosphate crystals.", 'role': 'assistant'}]