Which of the following statements is/are correct?

• A

  The chemical processes in the production of steel from haematite ore involve reduction followed by oxidation

• B

  Lead is extracted from its chief ore galena by both carbon reduction as well as self-reduction

• C

  In Hall-Heroult process, the electrolyte used is a molten mixture of alumina and cryolite or fluorspar

• D

  Haematite, cassiterite and argentite are oxide ores