Which statement best explains why reaction rates generally increase with increasing temperature?

(a) Reaction rates increase with increasing temperature because, as temperature increases, a greater fraction of molecules have enough thermal energy to surmount the activation barrier.

(b) Reaction rates increase with increasing temperature because, as temperature increases, the pre-exponential factor of the rate constant increases.

(c) Reaction rates increase with increasing temperature because, as temperature increases, molecules decompose into their constitutent atoms, which can then form new bonds to form the products.