<prompt> The organism causing biliary duct obstruction?Clonorchis sinensisAnkylostoma duodenaleStrongyloides stercoralisEnterobius vermicularis  <response>: 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 