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
[{'content': 'All are true about CBD stones except \nSelect and explain. \nA. Associated with GB stones, 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: Choledocholithiasis CBD stones are classified by point of origin Found in 6-12% of patients with GB stones Retained stones discovered within 2 years of cholecystectomy Recurrent stones detected >2 years following cholecystectomy Ref : Sabiston 20th edition Pgno :1494', 'role': 'assistant'}]