The correct answer is (b) Silicon.
Silicon is the most commonly used semi-conductive material because it is abundant, inexpensive, and has a wide range of properties that can be tailored to specific applications. Silicon is also a relatively stable material, which makes it ideal for use in long-lasting devices.
Selenium is a less common semi-conductive material that is used in some specialized applications. Selenium is more expensive than silicon and has a narrower range of properties.
Tin and iron are not semi-conductive materials. Tin is a metal that is used in a variety of applications, including solder and tin cans. Iron is also a metal that is used in a variety of applications, including construction and manufacturing.
Semiconductors are materials that have electrical conductivity between that of a conductor and an insulator. Semiconductors are used in a wide variety of electronic devices, including computers, cell phones, and solar panels.