Answer:
Increase the particle size of a reactant
Explanation:
Let me rewrite this question. I am assuming that it should be as follows,
If you _____ the particle size of a reactant then the reaction rate will increase because of the reactant's surface area is exposed allowing more particles to make contact with each other.
And, here we are being asked to fill this dash line _____
It could only be that the particle size increases or decreases. Increasing the size of the reactant will increase the chance of collisions if the container with which the reactants are kept are constant. This would increase the reaction rate - thus _____ = increases.
