Option-1 states that both statements I and II are individually true and that statement II is the correct explanation of statement I.

Statement I states that during the setting of cement, the structure has to be cooled by spraying water. This statement is true because the hydration process of cement generates heat, which can cause the temperature of the structure to rise. To control this temperature increase and prevent any damage to the structure, it is necessary to cool it by spraying water.

Statement II states that the constituents of cement undergo hydration during the setting of cement, and it is an exothermic reaction. This statement is also true. Hydration is the chemical reaction between cement and water, which results in the formation of crystals and the hardening of the cement. This reaction releases heat energy, making it an exothermic process.

The correct explanation is that the hydration process in statement II is the reason why the structure needs to be cooled in statement I. The release of heat during hydration necessitates the use of water cooling to maintain a stable temperature and prevent any structural damage.

Therefore, option-1 is the correct answer as it accurately asserts that both statements are true and that statement II provides the correct explanation for statement I.