The correct answer is C) Limestone.
Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3). It is used as a flux in the steelmaking industry to remove impurities from the molten iron. Limestone reacts with the impurities to form slag, which floats to the top of the molten iron and can be removed. This process helps to improve the quality of the steel.
Graphite is a form of carbon that is used as a lubricant, a conductor of electricity, and a component of batteries. Manganese is a metal that is used in the production of steel, batteries, and other alloys. Bauxite is an ore that is used to produce aluminum.
Graphite, manganese, and bauxite are not used as fluxes in the steelmaking industry.