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
Organism causing billiary duct obstruction: 
Select and explain. 
A. Clonorchis sinensis, B. Ankylostoma duodenale, C. Strongyloides stercales, D. Enterobius vermicularis
A: Clonorchis sinensis
Answer: A: Clonorchis sinensis 
Explanation: Hepatobiliary Parasitism
Common in Southern china
Biliary tract is infestated by adult helminthes or their ova
Causes :
Trematodes (Liver or biliary flukes) MC
Clonorchis sinensis
Opisthorchis viverrini or O. felineus
Fasciola hepatica
Nematode (Ascaris lumbricoides by intraductal migration of adult worm