Select the three main classes of worms in phylum Platyhelminthes.

The three main classes of worms in the phylum Platyhelminthes are:

1. Class Turbellaria: These are mostly free-living, aquatic flatworms, although some species are terrestrial or parasitic. The most well-known species in this class is the planarian.

2. Class Trematoda: Also known as flukes, these are parasitic flatworms that infect various species of vertebrates, including humans. They have complex life cycles that often involve two or more host species.

3. Class Cestoda: Commonly known as tapeworms, these are parasitic flatworms that live in the digestive systems of vertebrates. They have a unique body structure with a head, or scolex, used for attachment, and a series of segments that contain reproductive organs.

The three main classes of worms in the phylum Platyhelminthes are:

1. Class Turbellaria: These are mostly free-living, aquatic flatworms, although some species are terrestrial or parasitic. The most well-known species in this class is the planarian.

2. Class Trematoda: Also known as flukes, these are parasitic flatworms that infect various species of hosts. They have complex life cycles that often involve two or more hosts.

3. Class Cestoda: Commonly known as tapeworms, these are parasitic flatworms that live in the intestines of their hosts. They have a unique structure with a head, or scolex, used for attachment and a body composed of a series of segments called proglottids.

The three main classes of worms in the phylum Platyhelminthes are:

1. Class Turbellaria: These are mostly free-living worms, commonly found in marine, freshwater and terrestrial environments. The most well-known example is the planarian.

2. Class Trematoda: These are commonly known as flukes and are mostly parasitic. They have complex life cycles and often require more than one host. An example is the liver fluke.

3. Class Cestoda: These are commonly known as tapeworms. They are endoparasites, meaning they live inside the host. They are typically found in the intestines of their host. An example is the beef tapeworm.