This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parasitology, Subject name: Microbiology
Parasite causing biliary tract obstruction - 
Select and explain. 
A. Ascaris, B. Trichinella, C. Taenia solium, D. All of the above
A: Ascaris
Answer: A: Ascaris 
Explanation: Ans. is 'a' i.e., Ascaris * Infection of the biliary tract by adult helminths or their ova produces a chronic recurrent pyogenic cholangitis with or without multiple hepatic abscesses, ductal stones or biliary obstruction. The most commonly involved organisms are -# Clonorchis sinensis# lntrabiliary rupture of hydatid cysts of Echinococcus sp.# Intraductal migration of adult Ascaris lumbricoides.# Opisthorchis viverrini or O. felineus# Fasciola hepatica