What is a substance that reduces the amount of activation energy in a chemical reaction called?

catalyst
inhibitor
reactant
product

The answer is catalyst

Catalyst

Explanation: Catalyst is a substance which enhances the speed of Chemical reaction without consuming in the Reaction and it is regenerated after completion of Reaction and it is reused further cycle of reaction.

So catalyst reduces the activation energy by speed up the reaction

fe 55.85 g/mol and h2o 18.02 g/mol.