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
Renal stone formation is a multistep process that includes supersaturation of the urine, lack of inhibitory substances, and urinary stasis. Which type of renal calculi is associated with Proteus infection? 
Select and explain. 
A. Uric acid, B. Triple phosphate, C. Calcium oxalate, D. Xanthine
B: Triple phosphate
Answer: B: Triple phosphate 
Explanation: Struvite (magnesium-ammonium-phosphate) stones often are associated with infection by urea-splitting bacteria and are the most common cause of staghorn calculi, large stones that form a cast of the renal pelvis. Urea-splitting organisms, which include Proteus, Klebsiella, Staphylococcus species, Providencia, and Corynebacterium, also raise the pH of the urine (>7.2). Surgical treatment is recommended for staghorn calculi. Ref: Manthey D.E., Nicks B.A. (2011). Chapter 97. Urologic Stone Disease. In J.E. Tintinalli, J.S. Stapczynski, D.M. Cline, O.J. Ma, R.K. Cydulka, G.D. Meckler (Eds), Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e.