Which increases the rate of a chemical reaction?
a. a catalyst
b. a higher volume
c. a lower pressure
d. a lower temperature

I believe the correct answer from the choices listed above is option A. It is a catalyst that  increases the rate of a chemical reaction. It provides another pathway for the reaction in order for it to hasten the speed of the reaction. Hope this answers the question. 

1. o2(g)as a product