When these two air masses meet, moist air is forced ___. This causes water vapour to ___ as the air cools and rises, resulting in a band of heavy ___ around the globe.

• A. Upward, Evaporate, Fog
• B. Upward, Condense, Snow
• C. Downward, Evaporate, Fog
• D. Upward, Condense, Precipitation

Answer: (D)

When two air masses meet, the warmer, moist air is forced upward where the front acts as a boundary. As this air rises, it expands in the lower pressure of the upper atmosphere and cools (adiabatic cooling). When the temperature drops to the dew point, water vapor condenses into cloud droplets, producing condensation. This lifting and condensation along fronts lead to widespread, heavy precipitation around the globe, not just fog or evaporation. The other options don’t fit because evaporation isn’t what happens during frontal lifting, downward motion doesn’t cause the condensation that forms clouds, and fog is a near-surface phenomenon rather than a global band of precipitation.