Concept:Drying agents remove moisture from their surroundings due to their ability to absorb water.Explanation:Salts that act as drying agents possess the property of hygroscopy.Hygroscopic substances absorb water vapour from the air.This makes them useful in desiccators to keep materials dry.Examples include CaCl2 and ZnCl2.Efflorescence, high melting point, and low solubility do not explain this drying ability.Answer:C. hygroscopy