What is the starting substance fed into the electrolytic cell in Hall-Heroult process?

Cryolite Sodium hydroxide Aluminum hydroxide Alumina

Alumina

Hall-Heroult process is used to extract aluminum by using an electrolytic cell. Alumina means aluminum oxide. It is dissolved in cryolite, Na3AlF6, to increase electrical conductivity, reduce melting point and achieve greater yield of aluminum metal.