[Solved] The correct statement is:
During metallurgy of aluminium, when bauxite (powdered ore) is treated with concentrated NaOH, sodium aluminate (Na[Al(OH 4]) is formed and impurity (SiO 2) present in bauxite dissolves by forming sodium silicate (Na 2 SiO 3). The separation of the alumina from the impurities in the bauxite ore is usually accomplished by the Bayer Process.