I see that you did not list down any choices (or perhaps you forgot to include them) but it's ok, because I'm pretty sure that the answer is CONDENSATION.
It is the formation of liquid drops of water from water vapor. It is the process which creates clouds, making it necessary for weather activity.
On Earth's atmosphere, however, only 1% of it consists of water vapor.
The formed liquid water soon goes down to the surface through precipitation.
