Answer:
It means that it lowers the activation energy of a reaction and can be used again.
Step-by-step explanation:
A catalyst is a substance that allows the chemical reaction to occur at a faster rate or under different conditions (e.g. at a lower temperature) without being affected by the reaction.
The activation energy is the minimum energy required for the reaction to occur. Catalysts lower this energy and can be used again, which is why the last option is the correct one.