Answer the following question given this paragraph: 

At the beginning of the reaction, only the reactants A and B are present. Recall that over the course of a reaction, the reaction rate slows down. This is because the rate depends on the concentrations of one or more reactants. As the reactants are used up, their concentrations drop, thus decreasing the reaction rate.


Q: What happens to the reaction rate over the course of a reaction?


A:
slows down