Electro-magnets are created by...
A) Applying a charge to a magnetic material, wrapped in an insulator, which creates an electro magnetic field around the magnet.
B) Covering a magnet with insulation in applying an alternating electrical current to the magnet.
C) Twisting a ferromagnetic material, wrapping in an insulator, and applying a direct current to the coil.
D) Wrapping in insulated wire around a medal with ferromagnetic properties and applying an electric current.