if a catalyst lowers the activation energy, what raises the activation energy?\no heat\no a reaction\no…

Brief Explanations:

Activation energy is the minimum energy required for a chemical reaction to occur. Catalysts lower it to speed up reactions. Inhibitors work in the opposite way by increasing the activation energy, thus slowing down or preventing reactions. Heat generally provides energy to reactant molecules and can help them overcome the activation - energy barrier but doesn't raise the activation energy itself. A reaction doesn't raise activation energy. Another catalyst also lowers activation energy.

Answer:

D. an inhibitor