Final answer:
Cnidocytes (option B), known as stinging cells, are characteristic of jellies and are crucial for capturing prey and defending against predators.
Step-by-step explanation:
Cnidocytes are characteristic of jellies. The defining cell type for the cnidarians, which includes jellies, is the cnidocyte, known as the stinging cell. These cells play a crucial role in the organism's ability to capture prey or defend against predators. Cnidocytes are equipped with large stinging organelles called nematocysts, which function to immobilize or paralyze the target by releasing toxins.
The nematocysts contain barbs and a coiled thread that ejects with remarkable speed when the cnidocils, hairlike projections on the cell, are stimulated. This system allows jellies to be effective predators in their aquatic environments, despite their simple bodies lacking complex organs.