Answer the following question given this paragraph: 

rates The rates at which reactants are consumed and products are formed during chemical reactions vary greatly. We can identify five factors that affect the rates of chemical reactions: the chemical nature of the reacting substances, the state of subdivision (one large lump versus many small particles) of the reactants, the temperature of the reactants, the concentration of the reactants, and the presence of a catalyst.


Q: The presence of what, which acts as a trigger, affects the rate of chemical reaction?

 Choices:

- friction

- heat

- light

- catalyst

A:
catalyst
