Answer: increasing the temperature of the reactant mixture
Step-by-step explanation:
According to the collision theory , the number of collisions that take place per unit volume of the reaction mixture is called collision frequency. The effective collisions are ones which result into the formation of products.
It depends on energy factor: For collision to be effective, the colliding molecules must have energy more than a particular value called as threshold energy.
Thus increasing the temperature of the reactant mixture, the reactant molecules will gain kinetic energy and thus will increase the number of effective collisions.