A good drying agent is a substance used to remove moisture or water from a solution or compound. A drying agent should be hygroscopic, which means that it should have the ability to absorb or adsorb water molecules from the surroundings. This makes it effective in removing water from a compound or solution. Deliquescent compounds are those that absorb water so vigorously from the atmosphere that they dissolve in their own water of crystallization. Effervescent compounds release gas upon contact with water, while efflorescent compounds lose water of crystallization upon exposure to air. Therefore, the correct option for a good drying agent is hygroscopic.