What is the physical significance of the dry adiabatic lapse rate in the water cycle?

Correct answer: It is the rate at which unsaturated rising air cools without condensation

Correct answer: B. The dry adiabatic lapse rate describes how the temperature of an unsaturated air parcel changes as it rises or sinks without exchanging heat with its surroundings. Rising air enters regions of lower pressure, expands and cools because it does work during expansion. For dry air, the average cooling rate is about 9.8°C per kilometre, although the actual value can vary slightly with conditions. “Dry” here means unsaturated, not necessarily that the air contains no water vapour. If rising air cools to its dew point, condensation can begin; above that level, the moist adiabatic rate usually differs because latent heat is released. A is about phase change in water, C concerns soil and groundwater movement, and D concerns plant physiology. Memory cue: dry rising air expands and cools at roughly 9.8°C per kilometre.