In the cement industry, limestone is used in large quantities. Limestone is a sedimentary rock that contains calcium carbonate, which is a key ingredient in the production of cement. When limestone is heated at high temperatures, it undergoes a chemical reaction called calcination, where it breaks down into lime (calcium oxide). This lime, along with other materials, such as clay and silica, is then mixed with water and ground into a fine powder to create cement. Limestone is abundant and widely available, which makes it a cost-effective and sustainable choice for the cement industry. The option "Gypsum" (option 1) is used as a additive in small quantities to control the setting time of cement, whereas coal (option 3) is used as a fuel in the cement kilns. Clay (option 4) is used as a raw material, but not in large quantities as limestone.