The potential energy of an object is given by the formula \( PE = mgh \), where \( m \) is the mass of the object, \( g \) is the acceleration due to gravity, and \( h \) is the height above a reference point.
In the context of Kendra rolling her toy cars down a hill, the potential energy is highest when the cars are at the highest point on the hill. Therefore, the correct answer would be:
the cars with the greatest height.
At this point, the cars have the maximum potential energy, which will convert to kinetic energy as they roll down the hill.