The correct answer is D) Limestone.
Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3). It is the most common type of rock found in the Earth’s crust and is used in a variety of industries, including the cement industry.
Silica (SiO2) is the second most abundant mineral in the Earth’s crust, but it is not used in the cement industry. Magnesite (MgCO3) is a magnesium carbonate mineral that is used in the production of magnesium metal and magnesium oxide. Coal is a fossil fuel that is used to generate electricity.
Limestone is used in the cement industry because it is a source of calcium carbonate. Calcium carbonate is a key ingredient in cement, which is a binding agent that is used to hold concrete together. Limestone is also a source of other minerals that are used in cement, such as silica and alumina.
Limestone is found in abundance in Karnataka. The state has large reserves of limestone, which are used to produce cement and other building materials. The limestone industry is a major contributor to the economy of Karnataka.