The correct answer is C. Gamma rays.
Gamma rays have the highest frequency of all the electromagnetic waves. They are a type of high-energy radiation that is produced by radioactive decay. Gamma rays have a wavelength of less than 0.01 nanometers and a frequency of more than 300 petahertz.
Radio waves have a wavelength of 1 millimeter to 100 kilometers and a frequency of 30 hertz to 300 gigahertz. Microwaves have a wavelength of 1 millimeter to 1 meter and a frequency of 300 gigahertz to 300 terahertz. Light waves have a wavelength of 400 nanometers to 700 nanometers and a frequency of 400 terahertz to 700 terahertz.
The frequency of a wave is the number of waves that pass a given point in a given amount of time. The higher the frequency, the shorter the wavelength.