the stoichiometric ratios in option C are not reflective of the diagram/graph. We see the change to be equal in amount for all constituents so D is correct. What most likely happened was a change in decrease pressure which caused all of the species to decrease in concentration rapidly. in order to increase the number of molecules, you would shift to the side with the most moles eliminating A and B as they are equal. this is seen in D and C, but as I said C shows a change that isn't reflective of the graph, leaving D.