A student designed an experiment to determine how the concentration of an enzyme affected the rate of a reaction. She measured the rate of the reaction in test tubes with three different enzyme concentrations. She kept the other quantities, substances, and temperature the same for each test tube. To improve the experiment, the student should have . Question 15 options: Chosen a fixed reaction time and adjusted the quantity of enzyme to match the reaction time. Allowed each test tube to react at different temperatures. Designed an experiment with more clearly defined independent and dependent variables. Run one test tube with no enzyme but kept all other factors the same