The correct answer is: D. Wrought iron
Wrought iron is the purest form of iron. It is a soft, malleable iron that is made by repeatedly heating and hammering pig iron. The hammering removes impurities from the iron and makes it more ductile. Wrought iron is used to make a variety of products, including nails, chains, and decorative ironwork.
Cast iron is a hard, brittle iron that is made by melting pig iron and pouring it into a mold. Cast iron is used to make a variety of products, including cookware, engine blocks, and railroad tracks.
Steel is a strong, durable iron that is made by adding carbon to pig iron. Steel is used to make a variety of products, including cars, buildings, and bridges.
Pig iron is a hard, brittle iron that is produced from iron ore. Pig iron is used
to make a variety of products, including steel, cast iron, and wrought iron.