In what way does a catalyst increase the rate of a chemical reaction? it increases the concentration of reactants. it reacts with a portion of the reactant particles. it provides additional kinetic energy to reactant particles. it lowers the activation-energy barrier.

I THINK you answered the question yourself after the question mark just the last part.
a catalyst works when it lowers the activation energy of a reaction required in order to begin the reaction more quickly and also promotes effective collisions and a catalyst does this without reacting itself and can be used again later. different reactions require different catalyst

The answers are 3.c kelvin4.b liquids only