100 brainliest if correct

which is usually associated with a slower reaction rate?
a. adding a catalyst to the reactants
b. using a crushed solid in the reactants
c. using a strong solution of the reactants
d. removing heat energy from the reactants

It's D) removing heat energy from reactants

I can't explain it any better than this source than Google

“This is due to an increase in the number of particles that have the minimum energy required. The reaction rate decreases with a decrease in temperature. Catalysts can lower the activation energy and increase the reaction rate without being consumed in the reaction.”