Answer:
Enzyme: lactase
Substrate: lactose
Explanation:
Enzymes are proteins that catalyze reactions. That means that enzymes make reactions to occur faster. Usually, the name of an enzyme is ended with the suffix -ase. Thus, in this scenario, the enzyme is lactase.
The substrate of an enzyme is the molecule which binds to the active site of the enzyme. So, the enzyme acts upon the substrate. In this case, the substrate is lactose, which is a sugar.
Therefore, the enzyme lactase acts upon the substrate lactose and accelerates the reaction of degradation of this sugar.