Which among the following statement(s) is (are) true for the extraction of aluminium from bauxite?

• Correct answer
  A

  Hydrated ${\mathrm{Al}}_2{\mathrm{O}}_3$ precipitates, when ${\mathrm{CO}}_2$ is bubbled through a solution of sodium aluminate.
• Correct answer
  B

  Addition of ${\mathrm{Na}}_3{\mathrm{AlF}}_6$ lowers the melting point of alumina.
• Correct answer
  C

  ${\mathrm{CO}}_2$ is evolved at the anode during electrolysis.
• Correct answer
  D

  The cathode is a steel vessel with a lining of carbon.

Hence, the correct answer is options: 'A', 'B', 'C', 'D'.