The correct option is A Bile duct of sheep
Fasciola hepatica lives as an endoparasite in the bile passages of sheep. sheep acquire the infection by eating vegetation containing metacercaria. After ingestion, the metacercariae excyst in the duodenum and migrate through the intestinal wall, the peritoneal cavity, the liver parenchyma and at last settle in the biliary ducts where they develop into adult flukes. So the correct answer is 'bile duct of sheep'.