Suppose you are investigating how the amount of exercise a hamster gets affects how long the hamster lives. in order to control the experiment, which of these should you do? a. give all the hamsters the exact same diet. b. compare how long hamsters live to how long mice live. c. have your friend do the same experiment with hamsters that you are doing. d. make all the hamsters run on a hamster wheel for the same amount of time.