Answer:
Activation energy.
Explanation:
Activation energy may be defined as the minimum amount of energy required for the conversion of the reactant to the product. The reaction must have least activation energy to convert the reactant into product.
The reactant must pass this activation energy to convert them into the product. Catalysts are used in the reaction to lowers this activation energy and increases the rate of the chemical energy. The activation energy acts as the thermodynamic barrier that hinders the conversion of substrate into product.
Thus, the correct answer is option (A).
