According to the collision theory, only the effective collisions among the reacting species result in the products. In order that the collisions may be effective, the reacting species must have energy equal to or more than a certain minimum energy called threshold energy `(E^(@))`. Extra energy which has be supplied to the reactants to make collisions effective is known as activation energy `(E_(a))`. This is related to reaction rate with the help of Arrhenius equation, `k=Ae^(-Ea//RT)` The equation also helps in calculating the activation energy for a reaction at a specific temperature. In general, the rate of reaction is inversely proportional to the activation energy required. An increase in reaction rate with rise in temperature is due toA. an increase in the number of collisonsB. an increase in the number of activated molecules.C. lowering the activation energyD. shortening of mean free path.