The correct option is B Metal oxide
Roasting is a process of heating the concentrated ore at the temperature below its melting point in the presence of air. Sulphide ores are converted into its oxide by this process.
For example, zinc sulphide is converted to zinc oxide by heating it in the presence of oxygen. The reaction involved is given below:
2ZnS(s)+3O2(g)→2ZnO(s)+ 2SO2(g)