The change in energy during a reaction is represented in the following energy profile diagram - VCE - SSCE Chemistry - Question 3 - 2009 - Paper 1

In the context of the energy profile diagram, ΔE indicates the energy difference between the reactants and products in a chemical reaction. This energy change can represent the activation energy required to transform reactants into products and vice versa.

In this case, since the question is asking about the energy change labelled as ΔE, we need to focus on the activation energy that is necessary for the reverse reaction to occur. This corresponds to the energy barrier that reactants must overcome to revert back to their original state after forming products. Hence, the correct answer is C.