The correct answer is: b) Limestone.
Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3). It is the most common type of limestone in the world, and it is used in a variety of industries, including the cement industry. Limestone is used in cement because it is a source of calcium oxide (CaO), which is one of the main ingredients in cement.
Granite is an igneous rock composed of quartz, feldspar, and mica. It is a very hard rock, and it is not used in the cement industry.
Iron ore is a mineral that contains iron. It is used in the iron and steel industry to make iron and steel.
Bauxite is an ore of aluminum. It is used in the aluminum industry to make aluminum.
In conclusion, the correct answer is: b) Limestone. Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3). It is the most common type of limestone in the world, and it is used in a variety of industries, including the cement industry. Limestone is used in cement because it is a source of calcium oxide (CaO), which is one of the main ingredients in cement.