Question

how does a catalyst increase the rate of a reaction?
lowering the δh
increasing the frequency of collisions and the proportion of molecules with sufficient energy, the eₐ
lowering the eₐ
increasing the proportion of molecules with sufficient energy, the δh

Explanation:

A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy ($E_a$). It does not change the $\Delta H$ of the reaction. Increasing the frequency of collisions and proportion of molecules with sufficient energy is related to factors like temperature and concentration changes, not directly to what a catalyst does. A catalyst lowers the activation - energy barrier that reactant molecules must overcome to form products.

Answer:

Lowering the $E_a$