The tapeworm is in the categoryGroup of answer choicesNematodesCestodesTrematodes

The tapeworm falls under the category of Cestodes.

Explanation

1. Nematodes: This group includes roundworms, which are distinct from tapeworms. They have a cylindrical body and are different in structure and life cycle.

2. Cestodes: Tapeworms are flat, segmented worms that belong to this category. They are known for their long, flat bodies that can grow significantly in weight over time. Cestodes are typically parasitic and inhabit the intestines of vertebrates.

3. Trematodes: Also known as flukes, this group comprises flatworms that often have a leaf-like shape. They are different from tapeworms and have varied life cycles, often requiring multiple hosts.

In summary, tapeworms, with their unique body structure and lifecycles, are classified as Cestodes.