Answer: Option (A) is the correct answer.
Step-by-step explanation:
An inhibitor is defined as a substance which stops or inhibits the occurrence of a chemical reaction. So, an inhibitor basically slow down a chemical reaction by increasing the activation energy of the chemical reaction.
On the other hand, a catalyst helps in increasing the rate of a chemical reaction. This is because a catalyst lowers the activation energy and hence, more number of reactant molecules take part in the chemical reaction.
This causes an increase in the rate of a chemical reaction.
A substrate is a substance at which an enzyme acts. Basically, an enzyme binds to the active site of substrate.
So, in the given reaction energy of reaction A is more than reaction B.
Thus, we can conclude that in the given graph an inhibitor is being used in reaction A.