A girl in a black tank top and gray capri pants rides a bicycle past a pedestrian in a green shirt.
A girl rode a bike past a pedestrian.
However, case studies, like any other method GAO uses, have to meet two other criteria of  accuracy and lack of bias, in the sense that the evaluator's personal, preconceived opinions about a situation do not distort reporting and that the evaluator is scrupulously evenhanded in examining all sides of a situation.