What does the energy hill represent on an energy diagram?

The correct answer is option D.

Explanation:

When a chemical reaction proceeds the reactants are converted into products. The energy hill represents the potential energy of the reaction.

There are two conditions: If the reaction is endothermic than the energy of the products is greater than the energy of the reactants and  ΔH  is positive. This energy gain is shown in the form of a peak.  In an exothermic reaction, the energy of the products is lower than the reactants and  ΔH  is negative.

So the suitable option is D which states that the reaction is endothermic and the potential energy gained by the products is higher when a reaction proceeds.