The scenario described relates to the behavior of gases and how changes in temperature affect volume and pressure. Specifically, as the temperature of the gas within the balloon increases, the particles move faster, resulting in an expansion of the balloon. This behavior is best explained by Charles's Law.
Charles's Law states that the volume of a gas is directly proportional to its absolute temperature when the pressure is held constant. Thus, as the temperature increases, the volume of the gas (and hence the balloon) also increases.
So, the correct statement would be: "This illustrates Charles's Law, which shows that temperature and volume are directly proportional."