At which one of the following condition, a reducing agent is suitable for reducing a metal oxide

A metal whose Δf0G of  oxide is more negative acts like a reducing agent to the other metal oxide whose Δf0G of oxide is less negative;Δ0Gof the net reaction will be negative.          Ex: 2Cu(s)+O2(g)→Cu2O(s) ; Δf0G=less−ve;        … (1)                 2Mg(s)+O2(g)→MgO(s) ; Δf0G=more−ve;      … (2)         Equation (2) – Equation (1)          2Mg(s)+Cu2O(s)→2MgO(s) + 2Cu(s); Δ0G=−ve         Thus ‘Mg’ can reduce Cu2O;