The correct answer is option 'B' - the leeward side of the mountain.

A rain shadow zone refers to the area on the leeward side of a mountain where there is significantly less precipitation compared to the windward side. This phenomenon occurs due to the process of orographic precipitation.

Here is an explanation of the answer in detail:

1. Orographic Precipitation:
- Orographic precipitation is a weather phenomenon that occurs when air is forced to rise over mountains.
- As the air rises, it cools and condenses, leading to the formation of clouds and ultimately precipitation.
- The windward side of the mountain is the side that faces the prevailing wind, and it experiences the majority of orographic precipitation.

2. Windward Side of the Mountain:
- The windward side of the mountain refers to the side that faces the oncoming wind.
- As moist air is forced to ascend the windward slope, it cools and releases moisture, resulting in abundant rainfall.
- This side of the mountain is typically lush and green, with a higher amount of precipitation.

3. Leeward Side of the Mountain:
- The leeward side, also known as the "rain shadow" side, is the opposite side of the mountain from the windward side.
- As the air moves over the mountain and descends on the leeward side, it becomes warmer and drier.
- The descending air mass absorbs moisture, leading to a decrease in cloud formation and precipitation.
- Consequently, the leeward side of the mountain experiences significantly less rainfall and is often arid or semi-arid.

4. Characteristics of the Rain Shadow Zone:
- The rain shadow zone is characterized by lower rainfall and drier conditions compared to the windward side.
- The lack of consistent precipitation in this region affects vegetation growth and can lead to the formation of deserts or dry grasslands.
- The rain shadow effect can also impact local climate patterns, creating distinct microclimates within a region.

Overall, understanding the concept of a rain shadow zone helps explain the significant differences in precipitation and climatic conditions between the windward and leeward sides of mountains.