Boyle's Law states that the pressure of a gas is inversely proportional to its volume when temperature remains constant, which means that as the pressure decreases, the volume must increase to keep the equation balanced. This relationship can be expressed mathematically as P1V1 = P2V2, where P represents pressure and V represents volume.
When pressure in a closed container decreases, the particles of gas have more space to move around, leading to an increase in volume. This behavior is fundamental in understanding gas behavior in different conditions and can be observed in practical applications, such as in syringes or other sealed gas systems. Hence, when the pressure is reduced, the volume indeed increases, confirming the correct choice.