I need help with a science evolution and natural selection lab please help 02.04 Evolution and Natural Selection

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products