In curing cement plasters, water is sprinkled from time-to-time. This helps in :

Aluminum hydroxide fills the spaces between the calcium silicate particles to make the mass impermeable, while calcium hydroxide bonds the calcium silicate particles together. We can therefore deduce that water is occasionally sprayed over cement plasters to aid in the development of interconnecting needle-like crystals of hydrated silicates.

Thus the option C is correct.