Final answer:
The most appropriate control for a steady-state enzyme kinetics experiment would be gelatin without any enzyme solution, to establish a baseline for comparison.
Step-by-step explanation:
In a steady-state enzyme kinetics experiment, the most appropriate control would be a test tube containing the gelatin without any enzyme solution. This acts as a baseline to show the effects of the enzyme on the gelatin. By comparing the enzyme-treated gelatin to the control (gelatin without the enzyme), researchers can observe the influence of the enzyme on the substrate (gelatin) to confirm that any change in the system is due to the enzyme's activity.