The amount of pollution produced by cars was measured for cars using gasoline containing different amounts of lead. One car was used to test the four types of fuel: 10% lead gasoline, 15% lead gasoline, 20% lead gasoline, unleaded gasoline. In between the use of each the car's gas tank was emptied. The exhaust of the car was collected and analyzed. What is the independent variable?

The independent variable is the type of fuel

Explanation:

The independent variable in an experiment is the variable that is  being changed  in a scientific experiment. It is the cause of any of the observed outcomes of the experiment. The Independent variables is the variable that the experimenter changes to analyse its effect on the dependent variable(outcome).

In this case, the type of fuel (independent variable) is being changed and its effect on the amount of pollution (dependent variable) is observed.

cuz he's blad

explanation:

it is either c or d and i know for sure it is not a or b