As altitude increases, how does the behavior of gases in the atmosphere change?

As altitude increases, gases expand due to the decrease in atmospheric pressure. At higher altitudes, there is less air pressure because the weight of the air above becomes less. This reduced pressure allows the molecules of gas to spread out more, resulting in an increase in volume or expansion. Consequently, the behavior of gases is influenced directly by changes in pressure and temperature, which correlate with altitude. Therefore, the correct choice reflects the fundamental principle of gas behavior in different pressure environments, specifically emphasizing how gases respond to lower pressure conditions found at higher altitudes.