Answer: A) a catalyst
Step-by-step explanation:
A) Enzymes are also called as bio catalysts and thus increases the rtae of reaction in living beings.
A catalyst is a substance which increases the rate of a reaction by taking the reaction through a different path which involves lower activation energy and thus more molecules can cross the energy barrier and convert to products.
B) An inhibitor decreases the rate of reaction.
C) an accelerator increases the rate of reaction.
D) a depressant decreases the rate of reaction.