The activation energy of a chemical reaction is

A. the energy that initiates the reaction.
B. must be removed from the mixture.
C. must be released from the mixture.
D. activates the catalyst.
E. is the difference in the energies of the starting materials and products.

Explanation:

The activation energy for the forward reaction is the amount of free energy that is required or must be added to the system to go from the energy level of the reactants of the reaction to the energy level of the transition state( transition from reactants to product).

We can say that it is the minimum amount of energy needed to start a chemical reaction

So the activation energy of a chemical reaction is the energy that initiates the reaction.

Enzymes increases the rate of a reaction by decreasing this activation energy.