In the $Hoop$ process for the refining of $Al$,the molten materials form three different layers and remain separated 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 to keep these layers separate in the cell
• C
  The three layers maintain different densities
• D
  These layers are maintained at different temperatures