Which of the following statement is correct based on Ellingham diagram.

In Ellingham’s diagram, a graph is plotted between Δf0G of oxide (y-axis) Vs temperature (T) ( x - axis )A) 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 negativeΔ0G;of 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;B) At certain temperature Δf0G formation of a metal oxide becomes positive. It indicates that above that temperature the metal oxide decomposes to metal and oxygen.          Ex: At about  500° C the Δf0G of HgO and Ag2O becomes positive. C) For certain metals like Zn and Mg in their Δf0G Vs T plot a sudden abrupt increase in Δf0G is observed this indicates melting of metal oxide.