In the commerical electrochemical process for aluminium extraction, the electrolyte used is :
A. `Al(OH)_(2)` is NaOH solution
B. An aqueous of `Al_(2)(SO_(4))_(3)`
C. A molten mixture of `Al_(2)O_(3)` and `Na_(3)AIF_(6)`
D. A molten mixture of `Al_(2)O_(3)` and `Al(OH)_(3)`