The correct answer would be C. The volume of the balloon will decrease. As depicted in Charles’ Law which states that volume and temperature are directly proportional to each other, when the pressure of the gas is at a constant. When this theory is applied, the balloon will decrease in volume when it is exposed to cold air because the gas pressure inside the balloon remains the same. It is easier to remember this concept with the equation V/T = K where V is volume, T is Temperature and K is constant pressure.