The correct option is A Trematoda
Trematoda is a class within the phylum Platyhelminthes. It includes two groups of parasitic flatworms, known as flukes. Tissue flukes which infect the bile ducts, liver and other biological tissues. This group includes the lung fluke, Paragonimus westermani and liver flukes, Fasciola hepatica. Blood flukes inhabit the blood in some stages of their life cycle. Blood flukes include species of the genus Schistosoma. Hence, option A is correct.