Which statement best explains the role of a
catalyst in a chemical reaction?
(1) a catalyst is added as an additional reactant
and is consumed but not regenerated.
(2) a catalyst limits the amount of reactants used.
(3) a catalyst changes the kinds of products produced.
(4) a catalyst provides an alternate reaction pathway
that requires less activation energy.

The answer is (4). If you look at a Maxwell-Boltzmann energy curve, you will see that lowering the activation energy will increase the proportion of molecules with sufficient energy for a successful reaction collision. Therefore, a reaction with lower activation energy will proceed more quickly. Often, this lower activation energy is obtained by another mechanistic pathway. Catalysts increase reaction speed through these two basic mechanisms.

The answer is b on plato.