To solve this problem, we need to understand the role of a catalyst in a chemical reaction.$\newline$A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.$\newline$Let's analyze how a catalyst affects different thermodynamic quantities:$\newline$• Entropy: A catalyst does not affect the entropy of the system. Entropy is a state function and is determined by the initial and final states of the system.$\newline$• Internal energy: A catalyst does not change the internal energy of the system. Internal energy is also a state function.$\newline$• Enthalpy: A catalyst does not alter the enthalpy change of the reaction. Enthalpy is another state function.$\newline$• Activation energy: A catalyst provides an alternative reaction pathway with a lower activation energy.$\newline$The activation energy is the minimum energy required for a reaction to occur, and a catalyst lowers this energy barrier,$\newline$allowing the reaction to proceed faster.$\newline$Therefore, the addition of a catalyst during a chemical reaction alters the activation energy.$\newline$This corresponds to Option 4.