# If the reaction rate at a given temperature becomes slower. then

$(A)\;\text{The free energy of activation is higher} \\ (B)\;\text{The free energy of activation is lower} \\(C)\;\text{The entropy changes} \\(D)\;\text{The initial concentration of the reactants remain constant .}$

As the reaction rate decrease at a given temperature therefore the energy of activation increase.
Slower reaction rate indicates higher energy of activation.
Hence A is the correct answer.
edited Feb 19