Which of the following is a characteristic of cestodes (tapeworms)?

Cestodes, commonly known as tapeworms, are distinguished by their flat, segmented bodies, which is a defining characteristic of this group of parasites. The segmentation in tapeworms is evident in their structure, where the body is divided into segments called proglottids. Each proglottid contains reproductive structures, allowing for the tapeworm to reproduce effectively within the host.

This unique morphology is crucial for their parasitic lifestyle, as it enables them to have a larger surface area for nutrient absorption directly from the host's intestines, bypassing the need for a digestive tract. While high reproductive rate and other features may apply to cestodes, the most distinctive and defining trait in classifying them is their flat and segmented body structure.