Answer:
The Type of Drink (Gatorade or Water)
Explanation:
The Independent variables which causes the measured difference or change in the output of the dependent variable. In an experiment, the treatment administered to subjects which will most likely result into differing output are called the independent variables. In the scenario described above, the independent variable is the type of drink taken by the athlete, this drink will cause a change on the output, (how far an athlete can run) which is the dependent variable in the experiment.