Final answer:
A fluke is classified within the Phylum Platyhelminthes, and more specifically within the Class Trematoda. These parasitic flatworms include species such as the common liver fluke, Fasciola hepatica.
Step-by-step explanation:
A fluke is classified within the Phylum Platyhelminthes, specifically within the Class Trematoda. The Phylum Platyhelminthes includes flatworms, which are acoelomate organisms that consist of both free-living and parasitic forms. Flukes are known for being parasitic flatworms that can infect various organs of their hosts, such as the liver. The common liver fluke, Fasciola hepatica, is a well-known example of a trematode parasite.
The other classes within Phylum Platyhelminthes are Turbellaria, which includes free-living flatworms; Monogenea, which includes parasitic flatworms like gill flukes; and Cestoda, which comprises tapeworms. The segmented worms that have male and female reproductive organs in each segment and use hooks to attach to the intestinal wall are known as Class Cestoda, not flukes.