Concept:A liver fluke needs two hosts to complete its life cycle: one definitive host and one intermediate host.
Explanation:The liver fluke,
Fasciola hepatica, is a parasitic flatworm that affects livestock.
Sheep serve as the definitive host because the adult fluke lives and reproduces in the sheep's liver and bile ducts.
Freshwater snails serve as the intermediate host because the larval stages of the fluke, such as miracidia and cercariae, develop inside the snail.
Since the liver fluke requires both organisms to complete its development, the correct hosts are the sheep and the snail.
Pigs are not typical hosts of the liver fluke, so the other options are incorrect.
Answer:C. sheep and snail