Here's a problem to solve: When 1 gram of water is evaporated, the volume of the water vapor increases but the mass remains constant. Why does the mass of the water remain constant?

Among the 4 following options, which is the correct answer?

- A: The temperature of the water remains constant.
 
- B: The pressure acting on the water remains constant.
 
- C: The number of atoms in the water remains constant.
 
- D: The distance between water molecules remains constant.
 