Which of the following parasites live in the bile duct of the host?

Liver flukes are a type of flatworm that specifically inhabit the bile ducts of the liver in their host. These parasites, known scientifically as flatworms, can cause various health issues in infected animals, including inflammation and blockage of bile flow, which can lead to further complications in liver function. They typically have a complex life cycle that involves freshwater snails and other aquatic organisms.

In contrast, tapeworms primarily reside in the intestines of their hosts rather than the bile ducts. Roundworms can be found in various locations within the host but are not specifically associated with the bile ducts. Hookworms, while parasitic and affecting the intestines, do not inhabit the bile ducts either. Therefore, liver flukes are uniquely adapted to thrive in the bile ducts, making them the correct answer to the question.