In the context of the Hall-Heroult process for the extraction of Al, which of the following statements is false ?

(a) In Hall-Heroult process for extraction of Al, carbon anode is oxidised to CO and CO2.(b) When Al2O3 is mixed with CaF2, it lowers the melting(c) Al3+ is reduced at cathode to form Al.(d) Here, Al2O3 is an electrolyte, undergoing the redox process.Na3AlF6 although is an electrolyte but serves as a solvent,not electrolyte.