The process that transforms vapour into a liquid is known as condensation (D).

The opposite (liquid to vapour) is evaporation (B).

If condensation is significant enough to form clouds heavily laden with water droplets, precipitation (C) will result.

Conduction (A) is the transfer of heat between two parts of a stationary system caused by a temperature difference between the parts. Convection, on the other hand, involves the transfer of heat by the circulation or movement of the heated parts of a liquid or gas such as in the atmosphere or asthenosphere.