Group 2, I reckon. They started off with 100 mL vegetable oil, and group 2 ended up with 10+ of that, they also had an increase in engine oil. It was supposed to decrease like all of the other groups, but instead it increased like none of the groups.
Converting solar energy does not affect the earth system
Answer:
It is a group designed to not be affected by any variables and to be used as a comparison to the other groups. It helps increase the reliability of your results, as it shows your independent variable is what made something happen in your experiment.