Final answer:
According to Charles's Law, if the temperature of a gas is halved while pressure remains constant, the volume of the gas is also halved.
Step-by-step explanation:
When considering what happens to the volume of a gas in a sealed container if the temperature is reduced to one-half the original temperature, while keeping pressure constant, we can refer to Charles's Law. This law states that the volume of a gas is directly proportional to its absolute temperature, assuming that the pressure and amount of gas remain constant. Therefore, if the temperature is reduced to one-half of its original value and the pressure remains constant, the volume will also reduce to one-half (Option C).