In a scientific experiment, the is the thing the experimenter deliberately changed while observing

Independent Variable. This variable is the factor that is changed deliberately for the purpose of the experiment and observing how the outcome is, which is the dependent variable (affected by the independent variable).

You not be doing this in a quiz. if you actually studied your work you would know the answer. the answer though is that they would use gdp per capita because it measures a smaller portion (person). this could show individual growth per person in the country.