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
[{'content': 'Brown pigment gallstones are formed due to: \nSelect and explain. \nA. Cholesterol supersaturation, B. Increased deconjugation of bilirubin glucuronides, C. Increased biliary bilirubin load, D. Increased pigment in bile', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Characteristics of different types of gallstones and major risk factors for cholesterol gallstones Cholesterol stones Brown pigment stone Black pigment stone Main composition Cholesterol 50% bilirubin >50% bilirubin Colour Yellow-grey Brown Dark Brown-black Aetiology Cholesterol supersaturation Increased deconjugation of bilirubin glucuronides Increased biliary bilirubin load Ref: J Gastrointestin Liver Dis March 2011 Vol. 20 No 1, 9-11.', 'role': 'assistant'}]