Answer
Ultraviolet rays
Work Step by Step
a) The wavelength of radio waves is 0.001 m to 10,000 m
b) The wavelength of ultraviolet light is 1m to 1 mm.
c) The wavelength of infrared is 1mm to 100um
d) Lastly, the wavelength of ultraviolet rays is 10nm to 400nm
Analyzing the other options, it's clear that ultraviolet is the type of electromagnetic radiation that has the smallest wavelength.