Which term describes an enzyme?
a. substrate b. reactant c. catalyst d. product

C. Catalyst.
An enzyme is a biological catalyst that speeds chemical processes.
A substrate is the substance that reacts in contact with an enzyme.

Enzymes are specific when reacting with a substrate. Enzymes react only with certain substrates. It is like:

Enzyme — Substrate

Resembles the relationship of:

Lock — Key

Cis correct i think