B) Moving.
To produce an electric current in a coil of wire, a magnetic field through the coil must be moving or changing. This is due to the phenomenon of electromagnetic induction, discovered by Michael Faraday in the early 19th century. When a magnetic field moves or changes relative to a coil of wire, it induces an electric current in the wire. This is the principle behind electric generators, which convert mechanical energy into electrical energy by rotating a coil of wire in a magnetic field. In contrast, a static magnetic field alone will not induce an electric current in a coil of wire.