Consider a Sample of Water in a Closed Container

Multiple Choice

Consider a sample of water in a closed container. When the physical process has reached equilibrium, what can we say about any specific water molecule?

A) If it was present in the liquid phase, then it will always remain in the liquid phase.
B) If it was present in the vapor phase, then it will always remain in the vapor phase.
C) It will sometimes be in the liquid phase and sometimes be in the vapor phase.
D) If it was present in the liquid phase, then it will always remain in the liquid phase, and if it was present in the vapor phase, then it will always remain in the vapor phase.