The correct answer is C. Garnet.
Garnet is a type of magnetic material that is normally used in bubble memories. Bubble memories are a type of non-volatile semiconductor memory that uses magnetic domains to store data. The magnetic domains are created by applying a magnetic field to a thin film of garnet. The domains can be moved around by applying an electric field, and they can be read by measuring the magnetic field they produce.
Magnetic cores are a type of magnetic material that was used in early computers. They are made up of small, doughnut-shaped pieces of ferromagnetic material, such as iron or nickel. The cores are arranged in a matrix, and each core can be magnetized in one of two directions. The direction of magnetization is used to store data.
Cobalt is a metal that is used in a variety of magnetic materials, including permanent magnets and magnetic recording media. It is a ferromagnetic material, which means that it can be magnetized.
Metallic materials are materials that are made up of atoms that are held together by metallic bonds. Metallic bonds are formed when the atoms in a metal share electrons. Metallic materials are good conductors of electricity and heat.
None of the above is not the correct answer.