In the $Hoop$ process for the refining of $Al$,the molten materials form three different layers and remain separate during electrolysis because ..........

• A
  The upper layer is connected to the cathode and the lower layer is connected to the anode.
• B
  There is a special arrangement in the cell to keep these layers separate.
• C
  The three layers maintain different densities.
• D
  These layers are maintained at different temperatures.