In the graph, what effect would adding a catalyst have on D? A. It would increase B. It would decrease C. It would stay the same D. You cannot tell from this graph.

From the graph given, the value of D is the difference between the energy of the reactants and that of the product. We need to note that the catalyst lowers down the activation energy but it has nothing to do with the energy before and after the reaction. Thus, D will stay the same.