Which of the following statement is incorrect regarding the metallurgy of aluminium by electrolystic method ?
A. Electrolyte is `Al_(2)O_(3)` dissolved in `Na_(2)AlF_(3)` containing a little of `CaF_(2)`
B. Bauxite ore is purified before carrying out the electrolysis
C. Aluminium being heavier than electrolyte floats over the surface of the latter
D. Anode consist of a number of graphite rods which are periodically replaced
