Answer:
<h2>C. The water molecules must gain kinetic energy.</h2>
Explanation:
When liquid water become water vapor, molecules move more, because they force between them is less strong. Notice that vapor water as lower consistency, it's like smoke where molecules can way anywhere, at this stage the force between molecules is not strong enough to maintain a ridig shape.
Now, at vapor stage, molecues have to gain more kinetic energy, because the least is the force between molecules, the more kinetic energy is gonna there.
Therefore, the right answer is C.
