Final answer:
In an enzyme liver lab, the substances present at the end of the reaction are called products, which are the correct answer to the question posed.
Step-by-step explanation:
The student's question relates to an enzyme activity lab typically conducted in a high school biology course. The correct answer to the question in the enzyme liver lab about the products is D) Products. To understand this, we need to know the difference between reactants and products in a chemical reaction. The reactants, or substrates, are the substances present at the beginning of the reaction and upon which the enzyme acts. The enzyme's active site binds to these substrates, forming an enzyme-substrate complex, and facilitates their transformation. The resulting substances at the end of the reaction are known as the products, which are released from the enzyme's active site, allowing the enzyme to catalyze additional reactions.