Concept:A semiconductor is a material whose electrical conductivity lies between that of a good conductor and a good insulator.
Explanation:Examine each material according to its ability to conduct electricity.
Copper is a pure metal, so it is an excellent conductor with very high conductivity.
Iron is also a metal and conducts electricity very easily.
Plastic is a good insulator because it strongly resists the flow of electric current.
None of these three materials has the intermediate conductivity required for a semiconductor.
Silicon, however, is a metalloid whose conductivity falls between that of a metal and an insulator.
This intermediate behaviour is exactly what defines a semiconductor.
Silicon can also be doped with impurities to alter its conductivity for use in electronic devices.
Therefore, among the options given, silicon is the correct semiconductor.
Answer:Silicon (Option B).