Correct Option: B

The two important raw materials used for the preparation of cement are :
➤ Limestone : The chemical formula of limestone is CaCO₃ and it is used in the manufacture of cement just to provide CaO.
➤ Clay : Clay is hydrated aluminium silicate and iron (iii) oxide having chemical formula Al₂O₃SiO₂Fe₂O₃.2H₂O. Thus, clay consists of aluminium oxide (Al₂O₃), silicon dioxide (SiO₂), and iron (iii) oxide (Fe₂O₃) along with water molecules. In addition of limestone and clay, gypsum is also used during preparation of cement. It is added into the cement to slow down the hardening of cement when water is added into it.