This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
[{'content': 'The organism causing biliary duct obstruction? \nSelect and explain. \nA. Clonorchis sinensis, B. Ankylostoma duodenale, C. Strongyloides stercoralis, D. Enterobius vermicularis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Hepatobiliary ParasitismCommon in Southern China Biliary tract is infested by adult helminths or their ovaCauses:Trematodes (Liver or biliary flukes): Most CommonClonorchis sinensisOpisthorchis viverrini or O. felineusFasciola hepaticaNematode (Ascaris lumbricoides by intraductal migration of adult worm)', 'role': 'assistant'}]