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: Surgery
[{'content': 'Renal stones which are laminated and irregular in outline are \nSelect and explain. \nA. Uric acid, B. Calcium oxalate, C. Struvite, D. Cystine', 'role': 'user'}, {'content': "Answer: B \nExplanation: Calcium oxalate stones are laminated and irregular in shape and covered with sharp projections which cause bleeding. The surface of these stones are thus discoloured by altered blood- brown in colour- mulberry stones Reference : page 1296 Bailey and Love's sho practice of surgery 25th edition", 'role': 'assistant'}]