A balloon is filled with helium at a pressure of 1 atm and a temperature of 273 K. If the balloon is taken to a higher altitude where the pressure is 0.5 atm and the temperature is 250 K, what happens to the volume of the balloon?

• A. The volume remains constant.
• B. The volume increases.
• C. The volume fluctuates.
• D. The volume decreases.

Answer: (B)