This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
Which is true about gallstones 
Select and explain. 
A. Pigment gallstones are most common, B. Bacterial nidus of infection may be seen, C. Even if asymptomatic gallbladder should be removed, D. They are mostly solitary
B: Bacterial nidus of infection may be seen
Answer: B: Bacterial nidus of infection may be seen 
Explanation: Recently bacterial infection has been shown to play the role in pathogenesis of gallstone, this adds to the growing pool of studies finding an infectious nidus in these gallstones Brown stones are related to bile statsis and infection Gram negative bacteria (E.coli and Klebsiella) secretes beta-glucuronidase, which deconjugate soluble conjugated bilirubin Free unconjugated bilirubin precipitates and combines with calcium and bile to form brown pigment stones. Stones from whenever static foreign bodies are present in the bole duct (stents or parasites such as clonorchis sinensis and Ascaris lumbricoides Ref: Sabiston 20th edition Pgno : 1492