Which sentence correctly explains the process and conditions needed for rain to form?

A. Rain only falls during thunderstorms and extreme weather in below freezing temperatures.

B. Ice crystals melt as they fall through a layer of warm air and then refreeze into a solid form as they fall.

C. Water vapor freezes into solid ice crystals, and the temperature of the air should be below freezing.

D. The temperature in the sky needs to be above freezing, and water vapor condenses into liquid water.