For which of the following crystalline substances does the solubility in water increase upto 32º C and then decrease rapidly ?

The substance with solubility that increases upto 32º C and then decreases rapidly is CaCl2.2H2O. This is because calcium chloride is more soluble than other compounds when temperatures are between 0 and 32 degree Celsius. It has a high solubility in water, however at temperatures above 32 degree Celsius, the solubility significantly decreases.