The correct answer is (d), tungsten. Tungsten is a very strong metal that can withstand high temperatures. It is also a good conductor of electricity, which is necessary for an electric bulb to work.
Magnesium is a light metal that is not very strong. It is also not a good conductor of electricity.
Iron is a strong metal, but it is not very good at conducting electricity. It is also not as heat-resistant as tungsten.
Nichrome is a nickel-chromium alloy that is a good conductor of electricity. It is also heat-resistant, but not as much as tungsten.
Tungsten is the best material for the filament of an electric bulb because it is strong, heat-resistant, and a good conductor of electricity.