Parasite causing biliary tract obstruction -

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