The right answer is B. proteins.
A catalyst is a chemical species (which may be a protein or a cation ...) that allows the implementation of catalysis. As it is not consumed during the chemical reaction, it is used in small quantities and does not appear in the equation of the balance of the reaction that it can accelerate.
A catalyst has the effect of modifying the very nature of the steps which make it possible to pass reagents to the products. However, it is not able to modify either the direction of the evolution of the system or its state of equilibrium. It only influences the chemical kinetics, accelerating a reaction or allowing one reaction to be preferred over another.
A catalyst is specific for one type of reaction, i.e. the same catalyst cannot be effective for all chemical reactions.
