All electromagnetic waves travel at the same speed in a vacuum. However, different kinds of electromagnetic waves have different wavelengths. For example, microwaves have longer wavelengths than visible light. How is it possible for both microwaves and visible light to travel at the same speed in a vacuum if they have different wavelengths?

a
The waves of visible light have less energy than microwaves.
b
Microwaves and visible light have different frequencies.
c
The distance between a point on one wave to the identical point on the next wave is the same for both microwaves and visible light.
d
Microwaves and visible light have the same energy.