The correct answer is (d), graphene. Graphene is a single layer of carbon atoms arranged in a hexagonal lattice. It is the thinnest material known to man, and it is also the strongest. Graphene is 200 times stronger than steel, and it is also more flexible and lightweight. It is a promising material for a variety of applications, including electronics, composites, and energy storage.
German silver is an alloy of copper, nickel, and zinc. It is a hard, corrosion-resistant material that is often used in jewelry and other decorative items. Brass is an alloy of copper and zinc. It is a strong, malleable material that is often used in plumbing and other applications where corrosion resistance is important. Steel is an alloy of iron and carbon. It is a strong, durable material that is used in a wide variety of applications, including construction, manufacturing, and transportation.
Graphene is the strongest material because of its unique structure. The carbon atoms in graphene are arranged in a hexagonal lattice, which gives the material its strength and flexibility. Graphene is also very thin, which makes it lightweight. These properties make graphene a promising material for a variety of applications.