Fact 1: Water vapor cooling causes that water vapor to condense.

Fact 2: All carcasses are chilled with cool air for 48 hours.

Given the two facts above, answer the question "What causes water vapor to condense?" with the following options: 
- water vapor exploding
 - water vapor heating up
 - water vapor disappearing
 - circulatory systems
 - aqueous solution
 - Heat energy
 - water vapor chilling
 - Evaporation


 

       water vapor chilling  