Final answer:
The necessary enzyme substrate combination for a reaction to take place is Catalase and Hydrogen Peroxide (H2O2).
Step-by-step explanation:
The necessary enzyme substrate combination for a reaction to take place is Catalase and Hydrogen Peroxide (H2O2). In the presence of catalase, hydrogen peroxide is converted into water and oxygen, as shown in Reaction 3. This conversion occurs because catalase enzyme is capable of removing a hydrogen atom from the H2O2 substrate, acting as an oxidizing agent. Therefore, option A, Catalase and H2O2, is the correct answer.