This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urology, Subject name: Anatomy
[{'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: Phosphate or struvite stones are infection stones associated with urea-splitting organisms i.e. Proteus, Pseudomonas, Providencia, Klebsiella, Staphylococci and Mycoplasma. The high ammonium concentration desired from urea-splitting organisms results in an alkaline urinary pH, required for the precipitation of phosphate crystals. Ref : Bailey & Love 25/e p1296', 'role': 'assistant'}]