This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oncology, Subject name: Medicine
[{'content': 'The following are risk factors for developing cholangiocarcinoma except - \nSelect and explain. \nA. Choledochal cyst, B. Cholelithiasis, C. Liver flukes, D. Working in the rubber industry', 'role': 'user'}, {'content': "Answer: D \nExplanation: Cholangiocarcinoma (CCA) is an uncommon tumour that can arise anywhere in the biliary tree, from the intrahepatic bile ducts (20-25% of cases) and the confluence of the right and left hepatic ducts at the liver hilum (50-60%) to the distal common bile duct (20%). It accounts for only 1.5% of all cancers but the incidence is increasing. The cause is unknown but thetumour is associated with gallstones, primary and secondary sclerosing cholangitis, Caroli's disease and choledochal cysts . ref Harrison 20th edition pg 567", 'role': 'assistant'}]