Ellingham diagram is a graphical representation of :

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> JEE Mains 2021

Ellingham diagram represents a graphs between the change in free energy \((\Delta G)\) and temperature.

An Ellingham diagram is a graph showing the temperature dependance of the stability for compounds. This analysis is usually used to evaluate the ease of reduction of metal oxides to metals.
This graph provides basis for considering the choice of reducing agent in reduction of oxides.

Option (c) is correct