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: Unknown
[{'content': 'Organism causing billiary duct obstruction: \nSelect and explain. \nA. Clonorchis sinensis, B. Ankylostoma duodenale, C. Strongyloides stercales, D. Enterobius vermicularis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Hepatobiliary Parasitism\nCommon in Southern china\nBiliary tract is infestated by adult helminthes or their ova\nCauses :\nTrematodes (Liver or biliary flukes) MC\nClonorchis sinensis\nOpisthorchis viverrini or O. felineus\nFasciola hepatica\nNematode (Ascaris lumbricoides by intraductal migration of adult worm', 'role': 'assistant'}]