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
Commonest stone in case of UTI 
Select and explain. 
A. Phosphate, B. Urate, C. Cysteine, D. Calcium oxalate
A: Phosphate
Answer: A: Phosphate 
Explanation: 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