Final answer:
An increase in the frequency of successful collisions is necessary to increase the rate of a reaction.
Step-by-step explanation:
According to collision theory, an increase in the rate of a reaction is caused by An increase in the frequency of successful collisions. A successful collision occurs when two reactants collide with enough energy and the correct orientation. If there is an increase in the number of collisions, an increase in the number of particles with enough energy to react, and/or an increase in particles with the correct orientation, the rate of reaction will increase.