Step 1: Ellingham Diagram. An Ellingham diagram illustrates the thermodynamic stability of metal oxides by plotting the change in Gibbs free energy against temperature for the reduction of these oxides.
Step 2: Analysis of C/C\(_2\)O Line. When the C/C\(_2\)O line is positioned below the metal oxide line on the Ellingham diagram, it indicates that carbon is capable of reducing the metal oxide to its metallic form. In this process, carbon is oxidized to carbon monoxide (CO), rather than carbon dioxide (CO\(_2\)).
Step 3: Conclusion. Consequently, CO (option 1) is the correct choice, as carbon is oxidized to CO during the reduction of the metal oxide.