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.The figure presents a line graph in the coordinate plane. The horizontal axis is labeled p H, and the numbers 0 through 14, in increments of 2, are indicated. The vertical axis is labeled Relative Activity, and no numbers are indicated along it, although the axis ends in an arrowhead. The line begins at the point p H 0 with 0 relative activity, and moves horizontally to the right to p H 1 and 0 relative activity. The line then slants upwards and to the right at a constant rate until p H 2, then slants sharply upwards and to the right at a fairly constant rate until its peak at p H 5. The line then slants sharply downwards and to the right at a constant rate until p H 6, where the relative activity is half that of the peak. The line continues to slant sharply downwards and to the right at a constant rate until p H 7, where the relative activity is one tenth that of the peak. The line then slants less sharply downwards, and to the right at a constant rate until p H 9, where the relative activity is almost 0. The line then slants slightly downwards and to the right at an extremely low constant rate until p H 12 and p H 14, where relative activity drops to 0.Figure 1. The effect of pH on peroxidase activityOne 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?

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