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
Radiography of the following renal stones shows opacity, EXCEPT: 
Select and explain. 
A. Oxalate, B. Uric acid, C. Cystine, D. Struvite
B: Uric acid
Answer: B: Uric acid 
Explanation: Uric acid stones are the only radiolucent stone. Kidney Stones: Composition Radiographic Appearance Disease Association(s) Calcium oxalate and calcium phosphate Radiopaque Parathyroid gland hyperplasia, sarcoidosis Uric acid Radiolucent Gout, leukemia, and lymphoma Struvite (triple stones made of magnesium, phosphate and ammonium) Radiopaque Xanthogranulomatous pyelonephritis Cystine Radiopaque Ref: Wyatt C., Butterwoh IV J.F., Moos P.J., Mackey D.C., Brown T.G. (2008). Chapter 16. Pathology of the Kidney and Bladder. In C. Wyatt, J.F. Butterwoh IV, P.J. Moos, D.C. Mackey, T.G. Brown (Eds), Pathology: The Big Picture.