Which action will slow down the rate of a reaction? a. decreasing surface area of a solid reactant b. adding a catalyst to the reaction c. increasing the concentration of the reactants d. raising the temperature of the reactants

(A) is the correct choice

As we increase the surface area of the reactants, we increase the rate of reaction.

Increasing the surface area of a solid reactant exposes more of its particles to attack. This results in an increased chance of collisions between reactant particles, so there are more collisions in any given time and the rate of reaction increases.