Give Reason:
a. Prior to reduction of the metal, sulphides and metal carbonates must be converted into metal oxides.
b. for extracting some metals, displacement reactions are used instead of carbon to obtain metals from their oxides.

Explanation

a. It is eaiser to obtain metal from its oxide than form its sulphides and carbionates.
b. The oxide of metals comparatively more reactive than zinc are very stable, hence they cannot be reduced using carbon.