This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gall Bladder & Bile Ducts, Subject name: Surgery
[{'content': 'All are true bout CBD stones except: \nSelect and explain. \nA. Associated with GB stones in 10% cases, B. Primary stones are usually brown, C. Laboratory values may be normal in one third cases of choledocholithiasis, D. Retained stones are discovered after 2 years of cholecystectomy', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) Retained stones are discovered after 2 years of cholecystectomy* Recurrent stone: discovered after 2 years after Cholecystectomy* Retained stone: discovered within 2 years after cholecystectomy', 'role': 'assistant'}]