The correct answer is: a) Cement.
Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3). It is the most common sedimentary rock on Earth, and it is used in a variety of industries, including cement, steel, fertilizer, and paper.
Cement is a binding agent that is used to hold together aggregates (sand, gravel, crushed stone) to form concrete. It is made by heating limestone and clay to a high temperature, and then grinding the resulting clinker into a powder. The powder is then mixed with water and other ingredients to form concrete.
Steel is an alloy of iron and carbon. It is the most widely used metal in the world, and it is used in a variety of products, including buildings, bridges, cars, and appliances. Steel is made by melting iron ore and then adding carbon to the molten iron. The carbon content of steel determines its strength and properties.
Fertilizer is a substance that is added to soil to improve crop yields. It is made from a variety of materials, including limestone, phosphate rock, and potash. Limestone is used in the production of phosphate fertilizer.
Paper is a thin, flexible material that is made from wood pulp. It is used in a variety of products, including books, newspapers, magazines, and packaging. Wood pulp is made from wood that has been ground into a fine powder. The powder is then mixed with water and other ingredients to form a slurry. The slurry is then spread onto a moving belt, where it is dried and pressed into sheets of paper.
In conclusion, the correct answer is: a) Cement. Limestone is an important raw material for the production of cement.