In the $Bessemer$ and $open-hearth$ process for the manufacture of steel,which one of the following is used for the removal of carbon in part or whole?
$Bessemer \to$ $Open-hearth$

• A
  $Ferric \ oxide \to$ $Air$
• B
  $Air \to$ $Ferric \ oxide$
• C
  $Oxygen \to$ $Scrap \ iron$
• D
  $Air \to$ $Scrap \ iron$