In Addition to the Electric Force Law and the Magnetic

In addition to the electric force law and the magnetic force law, the other key principle that is needed to explain electromagnetic waves is

A) Newton's law of motion.
B) electromagnetic fields are established instantaneously.
C) electromagnetic forces can be felt across a distance.
D) forces always come in pairs, so for every sender of electromagnetic force there must be a receiver.
E) electromagnetic fields are not established instantaneously.