In major global climate classification systems (such as Köppen), which climate zone group is primarily defined by the annual balance of moisture, specifically where potential evapotranspiration exceeds average precipitation?

💡 Explanation:

The Dry Climates (Group B) are unique because their classification hinges on a moisture deficit (aridity), rather than the temperature or seasonality criteria used to define the A, C, D, and E groups. A region is defined as arid or semi-arid if the loss of water through evapotranspiration is greater than the water gained through precipitation.