Roasting of ores is done in

Options

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, in order to leave enough of sulphur to combine with arsenic, antimony etc. and to convert all the rion ad copper to oxides.
D. to melt arsenic and antimony sulphides etc. and remove them by liquation and to burn off sulpur partially to leave enough to combine with copper and iron.

Answer

C