The gas laws describe the behavior of gases under specific conditions of temperature, pressure, and volume. Three gas laws show the relationship between two variables when all others are held constant: Boyle’s law (pressure and volume are inversely proportional), Charles’s law (volume and temperature are directly proportional), and Gay-Lussac’s law (temperature and pressure are directly proportional).

Select the balloon volume that would represent the following conditions: the temperature decreases under constant pressure.

According to Charles's law, volume and temperature are directly proportional when pressure is held constant. This means that as temperature decreases, the volume of the gas will also decrease. Therefore, the balloon volume would decrease.