Final answer:
The highest frequency form of electromagnetic energy is ultraviolet. The correct answer is option c.
Step-by-step explanation:
The highest frequency form of electromagnetic energy among the given options is ultraviolet.
The electromagnetic spectrum ranges from high-frequency gamma rays to low-frequency radio waves. Visible light falls between ultraviolet and infrared light. Ultraviolet radiation starts with frequencies just above violet in the visible range and is produced primarily by electronic transitions in atoms and molecules.
In the given options, radio, visible light, and infrared have lower frequencies than ultraviolet.