Answer:
increasing the concentration of the reactants
Explanation:
Increasing the concentration of reactants usually increases the frequency of effective collisions between reactant molecule. This also results in the increase in the rate of a reaction . This is because as the concentration of the reactant is increased then more of the reacting molecules or ions are present to form the reaction products.
Increase in Temperature and Pressure of gaseous reactants results in the increase of the frequency of effective collisions between reactant molecules.