Answer: Option B
An oasis is a fertile area in the desert that usually has a supply of water, which allows plants and trees to grow. It can be thought of as an island in the desert, surrounded by a sea of sand.
Oases can be formed by natural springs or by digging wells to access underground water. The water in an oasis can come from a variety of sources, such as underground aquifers or rainwater that has collected in depressions or valleys.
The availability of water in an oasis attracts a variety of wildlife, as well as human settlements and travelers who need water to survive. Oases have historically been important as stopovers for trade caravans and for providing a place to rest and refuel for travelers crossing the desert.
In summary, an oasis is an area in the desert that is characterized by its supply of water, which allows for the growth of plants and trees. The presence of water in oases makes them an important resource for wildlife, human settlements, and travelers who need water to survive in the desert. Therefore, option B, water, is the correct answer to the question.