I believe it is D. Earth spinning on it's axis.
Answer:
12500 V
Explanation:
The electric field in the gap of a parallel-plate capacitor is uniform, so the following relationship between electric field strength, potential difference and distance can be used:

where
is the potential difference between the plates
E is the electric field strength
d is the distance between the plates
For the capacitor in this problem, we have


Substituting, we find

Answer:
Radio waves
Explanation:
Electromagnetic waves are produced by the oscillations of electric and magnetic field. They are transverse waves, which means that the oscillations occur in a direction perpendicular to the direction of propagation of the wave, and they are the only type of waves that can travel through a vacuum.
Electromagnetic waves are classified into 7 different types, depending on their frequencies. From lowest to highest frequencies, we have:
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
Radio waves are the electromagnetic waves with lowest frequency. They are used, for examples, for satellites, telecommunication, broadcasting.