Why does it rain more heavily on the windward side of mountain ranges?

A.Air masses absorb moisture as they increase in altitude, form clouds which precipitate rain.
B.Cool air on the lee side of the mountain encounters warm moist air from the windward side causing it to give up moisture.
C.Prevailing winds bring warm, moist air masses from sea level to high altitudes, cooling the air and causing rain.
D.Cool, moist air from the oceans warms over land and precipitates rain on the windward side of mountain ranges.