Why does NaCl have a higher melting point than NH3? a. NaCl exhibits network covalent bonding, which is the strongest type of bonding.
b. NaCl is an ionic substance and it requires a lot of energy to break ionic bonds.
c. NaCl is small and exhibits greater Coulombic attractive forces.

The answer is: C. The amount of water in the hydrosphere remains constant. 

The hydrosphere denotes the entire water available worldwide in lakes and streams, subsurface water, the ice of glaciers, and water vapor in the atmosphere. The water cycle is the process that converts liquid water to atmospheric water vapor (and vice versa) throughout the world.