In the commercial electrochemical process for aluminium extraction, the electrolyte used is
A. `Al(OH)_(3)` in NaOH solution
B. an aqueous solution of `Al_(2)(SO_(4))_(3)`
C. a molten mixture of `Al_(2)O_(3) and Na_(3)AlF_(6)`
D. a molten mixture of `AlO(OH) and Al(OH)_(3)`
