Researchers investigated the influence of environmental pH on the activity of peroxidase, an enzyme that catalyzes the conversion of hydrogen peroxide to water and oxygen gas. In an experiment, the researchers added a hydrogen peroxide solution containing guaiacol to several identical test tubes and adjusted the solution in each test tube to a different pH. The researchers included the guaiacol because it caused the solutions to change color as the reactions proceeded, which the researchers relied on for measuring reaction rates. Finally, the researchers added the same amount of peroxidase to each test tube and measured the rate of each reaction at 23°C. The results of the experiment are represented in Figure 1. One of the researchers proposes using oxygen gas production to measure reaction rates. Which of the following statements best justifies the use of the proposed modification as a way of creating an appropriate control for the investigation?
O the experiment can be repeated without hydrogen peroxide, which will help eliminate an uncontrolled variable. O the experiment can be repeated without hydrogen peroxide, which will help eliminate an uncontrolled variable. O the experiment can be repeated without peroxidase, which will introduce a second independent variable. O the experiment can be repeated without peroxidase, which will introduce a second independent variable. O the experiment can be repeated without guaiacol, which will reveal the effect of guaiacol on the reaction rates. O the experiment can be repeated without guaiacol, which will reveal the effect of guaiacol on the reaction rates. O the experiment can be repeated without water, which will reveal whether the reaction can occur inside a living cell.