The correct answer is: a) Cement.
Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3). It is the main raw material used in the production of cement. Cement is a binding agent that is used to hold together aggregates (sand, gravel, crushed stone) to form concrete. Concrete is one of the most widely used building materials in the world.
The presence of limestone deposits has led to the development of a significant cement industry in Andhra Pradesh. The state is home to several large cement plants, which produce cement for use in the construction industry. The cement industry is a major contributor to the economy of Andhra Pradesh.
The other options are incorrect because they are not directly related to the production of cement. Steel is made from iron ore, not limestone. Fertilizer is made from natural resources such as phosphate rock and potash. Glass is made from silica sand, soda ash, and lime.