The characteristic of a superconductor is zero permittivity (option C). Superconductors are materials that, when cooled below a specific critical temperature, exhibit no electrical resistance, meaning that electric current can flow through them without any energy loss. This zero resistance property is a defining feature of superconductors and distinguishes them from ordinary conductive materials. The absence of electrical resistance allows superconductors to maintain an electric current indefinitely without an external power source, which is not possible in materials with non-zero permittivity. Superconductors also exhibit the Meissner effect, which is the expulsion of magnetic fields from their interior, further distinguishing them from regular conductors. These properties have significant implications for various advanced technological applications, including powerful electromagnets used in MRI machines, maglev trains, and potentially for lossless power transmission in electrical grids.