if a catalyst lowers the activation energy, what raises the activation energy?\nheat\na reaction\nanother…

Brief Explanations:

A catalyst lowers activation energy to speed up a reaction. An inhibitor works in the opposite - it raises the activation energy, making the reaction less likely to occur by interfering with the reaction pathway. Heat generally provides energy to reactants and can lower the effective activation energy barrier in some cases by increasing the kinetic energy of reactant molecules. A reaction itself doesn't raise activation energy. Another catalyst also lowers activation energy.

Answer:

D. an inhibitor