(a) In collision theory, \(e^{-E_a / R T}\) corresponds to the fraction of molecules that have energy equal to or greater than \(E_a\) (activation - energy) is the correct statement because it is in accordance with Arrhenius theory.
(b) The number of collision of the reacting molecules per second per unit volume of the reaction mixture is activated complex is not a correct statement as activated complexes are formed during the reaction, which finally gives the product.
(c) Molecularity is the number of molecules involved in a complex reaction. This is also not correct as molecularity is defined as: The number of reacting species taking part in a reaction, which must collide simultancously in order to bring out the reaction.
(d) A catalyst, catalyses the non-spontaneous reaction. This is also not correct as a catalyst can catalyse the spontaneous as well as non-spontaneous reactions.
Hence, option (a) is the correct answer.