If relative humidity is low, why is soil kept in sunlight more likely to dry quickly?

Correct answer: Dry air can accept more vapour from soil

Correct answer: A. Low relative humidity means that the air contains substantially less water vapour than it could hold at its current temperature. Therefore, there is a larger capacity, or vapour-pressure deficit, for water to move from moist soil into the air. Sunlight supplies energy and warms the soil and its water, which generally increases the rate of evaporation. Wind can further remove moist air from the surface. B is the opposite of the truth: dry air usually supports faster evaporation, provided liquid water is available. C is wrong because sunlight normally promotes heating and evaporation, not condensation at the exposed soil surface. D is wrong because soil pores can contain water even when the surface appears dry. The exact rate also depends on soil texture, vegetation, wind, temperature, and available moisture, but low humidity and sunlight together create strong evaporative demand. Memory cue: warm surface plus dry air usually means faster drying.