What happens to warm, moist air when it is cooled?

When warm, moist air is cooled, the temperature drop reduces the air's capacity to hold moisture. As the air cools, it reaches a point known as the dew point, at which the water vapor in the air condenses into liquid water. This process results in the release of some moisture as condensation. This principle underlies many weather phenomena, such as cloud formation and fog, where water vapor cools and condenses into tiny droplets.

The other options describe various physical properties of air but do not accurately depict the behavior of warm, moist air upon cooling. For instance, while it is true that air can expand when warmed, cooling typically leads to contraction rather than expansion. Similarly, while some moisture may evaporate at various temperatures, the dominant effect during cooling is condensation, not evaporation. Lastly, while denser air generally sinks and less dense air rises, the cooling of air does not mean it becomes less dense; in fact, cooler air tends to become denser and thus sinks rather than rises. Thus, the release of moisture as condensation is the correct response to what happens to warm, moist air when it is cooled.