Roasting of copper pyrites ores is for the following purposes:

• A
  To burn off sulphur,arsenic,antimony etc. as oxides and convert all the iron and copper to their oxides.
• B
  To burn off arsenic,antimony etc. as oxides and burn off sulphur so that enough of it remains to combine with all the copper.
• C
  To burn off sulphur partially to leave enough to combine with arsenic,antimony etc. and to convert all the iron and copper to oxides.
• D
  To melt arsenic and antimony sulphides etc. and remove them by liquation and to burn off sulphur partially to leave enough to combine with copper and iron.