Which dissolved substance do aquatic animals release into their external environment as a result of cellular respiration?

this protocol describes a detailed procedure for intracellular flow cytometry staining.

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

c.           is the correct answer