Which statement is TRUE about ideal gas in a container?

• A. The volume of a gas is 0 L at 0°C, constant pressure, and at a fixed amount.
• B. The number of gas molecules decreases by 50% when the temperature changes from 400°C to 200°C at constant pressure and constant volume.
• C. The volume of a gas decreases by 50% when the temperature decreases from 80°C to 40°C at constant pressure and a fixed amount of gas.
• D. The volume of a gas doubles when the pressure changes from 2P to P at constant temperature and a fixed amount of gas.
• E. None of the above.

Answer: (D)