The correct answer is C) Aero light. Aero lights are not marked with a magenta circle on nautical charts, unlike radar transponder beacons (A), radar stations (B), and radio beacons (D), which are all marked with a magenta circle. This is in accordance with the conventions and symbols used on nautical charts, as defined by the National Oceanographic and Atmospheric Administration (NOAA) and other charting authorities. Aero lights, which are aviation-related lights, are marked on charts using a different symbol, typically a star or other aviation-specific symbol, rather than the magenta circle used for maritime aids to navigation.