The electrons in the outermost energy level are responsible for the atoms . These electrons are called the electrons. There can never be more than of these electrons.

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Answer is: hydrogen is being oxidized.chemical reaction: co₂ + h₂ → co + h₂o.oxidation half reaction: h₂ → 2h⁺ + 2e⁻.reduction half reaction: c⁺⁴ + 2e⁻ → c⁺².oxidation is increase of oxidation number, hydrogen change oxidation number from neutral charge (in molecule of hydrogen) to oxidation number +1 (in water).