Using the Fundamental Equation of Wave, we have:
Letter B
Here observer is moving along with an electrical charge
now magnetic field on a moving charge is given by equation

electrical force on a moving charge is given by formula

so here we can say when observer is moving with the charge it will have two forces on it
1. magnetic force due to existing magnetic field
2. electric force due to electric field
so here he must have to experience both type of field presence
So here correct answer must be
<em>C- electric and magnetic fields </em>
The first step would be to create an electromagnet. You can create an electromagnet by winding a copper wire around the nail, the connect both ends to the battery. A current would start flowing around the nail through the wire, creating an electromagnet with its own magnetic field. Next, bringing the electromagnet to the mixture of copper and iron would slowly attract the pieces of iron (as copper is weakly magnetic). Do this slowly and the iron pieces would all slowly be separated from the copper pieces.
C - because gravity is keeping them in orbit