Answer:
A
Step-by-step explanation:
A catalyst refers to an enzyme composed of peptides in their tertiary conformation.
The addition of a catalyst provides a new path to the reaction and the reaction proceeds in a faster way compared to the reaction without a catalyst.
The peptides are arranged in such a way that they form a pore-like structure which allows the binding of the substrate molecules by forming a temporary covalent bond. These bonds lower the activation energy of the complete reaction which is required to initiate a reaction.
In the given diagram, the activation reaction is represented by the letter "A" and therefore a catalyst will lower and alter the value of A.
Thus, Option-A is correct.