The independent variable is the exercise.
Answer: Option C
Explanation:
In a hypothesis done by the experimenters to reach to a conclusion and do researches, certain variables are used. Those variables are of two types, the independent variable and the dependent variable. The latter are dependent on the former in the researches done.
In the experiment in the question, the independent variable is the exercises done by the subjects and the people in the control groups which changes the mood of the people.
