What electrical component is typically constructed as a coil of wire?

An inductor is most commonly constructed by winding a length of wire into a coil. This coiled shape allows the magnetic fields generated by the current in each loop of the wire to overlap and concentrate. This concentration greatly increases the component's inductance compared to a straight piece of wire. While all wire has a tiny amount of natural resistance and inductance, a deliberate coil of wire is specifically designed to function as an inductor. Capacitors are built from parallel plates, diodes are made from semiconductor materials, and switches are mechanical contacts, making 'inductor' the only correct answer.