Question

how does a catalyst influence a chemical reaction?
it speeds up or slows down a chemical reaction by direct participation.
it reacts with products to increase the concentration of reactants.
it decreases the amount of energy necessary for the reaction to proceed.
it increases the total amount of products formed.

Explanation:

A catalyst lowers activation - energy, speeding up reaction without being consumed. It doesn't change amount of products or directly react with products.

Answer:

It decreases the amount of energy necessary for the reaction to proceed.