You want to test how the mass of a reactant affects the speed of a reaction. Which of the following is an example of a controlled experiment to test this?
O A. The mass of all the reactants is varied, and the time it takes the
reaction to finish is measured.
B. The mass of one reactant and the temperature of the reaction
mixture are increased until the reaction is finished.
C. The mass of one reactant at a time is varied, and the time it takes
the reaction to finish is measured.
D. The mass of all of the reactants is kept the same, and the mixtures
are allowed to react for different lengths of time.