An electric bulb has a filament made of ____.

The correct answer is Option (4) → Tungsten

The filament of a bulb gives light only when it is heated until it glows white-hot, at about 2,500°C or more. Tungsten is used because it has the highest melting point of all metals (about 3,422°C), a high resistance, and can be drawn into very thin wires. The bulb is filled with an inert gas such as argon, or emptied of air, so that the hot filament does not burn away.

Iron (melting point about 1,538°C), copper (about 1,085°C) and lead (about 327°C) would melt long before they glowed white-hot.