The right answer is Temperature (or decrease in heat energy).
Condensation is the physical phenomenon of a change in the state of matter from a gaseous state to a condensed state (solid or liquid). The transition from the gaseous state to the liquid state is also called liquefaction.
In nature, the condensation of water vapor is an important step in the water cycle.
We can experience this change of state during a shower where, in contact with the cold mirror, the water vapor in the air condenses into droplets.
