Step 1: Ellingham Diagram.
An Ellingham diagram is used to study the thermodynamic stability of metal oxides. It shows the variation of Gibbs free energy with temperature for the reduction of metal oxides.
Step 2: Analysis of C/C\(_2\)O Line.
If the C/C\(_2\)O line lies below the metal oxide line in the Ellingham diagram, it means that carbon can reduce the metal oxide to the metal, and the carbon itself will be oxidized to CO (carbon monoxide), not CO\(_2\).
Step 3: Conclusion.
Therefore, the correct answer is CO (option 1), as carbon is oxidized to CO when reducing the metal oxide.