David has a weather balloon that he fills with helium and then releases. As the balloon rises into the atmosphere, the balloon gets bigger and bigger. Why?
A) the temperature of the gas is decreasing, so the volume is increasing
B)the volume is increasing as the pressure inside is decreasing to match the air pressure outside the balloon
C)gas is leaking out of the balloon, so there isn't as much volume
D)this doesn't happen -- the balloon will actually stay the same size