You are flying over a mountain range and notice that the east facing slope of the range looks dry relative to the west facing slope.How could this be explained?

A) The east facing slope is not hit by prevailing winds. As a result descending air on the east facing slope is very dry.
B) The west facing slope is hit by prevailing winds. As a result the east facing slope gets a lot of rain.
C) There is no explanation.
D) The east facing slope is hit by prevailing winds. As a result all moisture is lost on the west facing slope.