Answer:
D) Radio waves
Explanation:
The electromagnetic spectrum is composed of electromagnetic waves that have all the same speed (the speed of light) but differ in how fast they vibrate in the perpendicular direction to their propagation vector, the slower they vibrate the less energy they have, they are more relaxed, and their wavelenght is longer. The radio waves are those in the spectrum of lesser energy (or longest wavelenght).
In the image it can be seen that the faster they vibrate the more energy they have, and they're classified in order of lesser to greater energies as: radio waves, microwaves, infrarred light, visible light, ultraviolet light, X-rays and gamma rays.
