Correct Answer - C
In the extraction of copper from its sulphide ore, the metal is formed by the reduction of `Cu_(2)O` with `Cu_(2)S`. This reaction completes with the process of autoreduction.
Chemical reaction occurring this reaction is as follows
`Ci_(2)O +(1)/(2)Cu_(2)Srarr 3Cu+(1)/(2)SO_(2)`
In this process, copper appears as blister copper.