Answer : 2. "Barkhan "
Explanation :

Barkhan: Barkhans are found between high and low hills. Sometimes they get scattered here and there too. In the Sahara desert, there is also a way to move between the barkhans, which are known as Ghasi and Caravan. Their shape is also half-moon shaped and arched. When the direction of the wind changes, the position of the cloud also changes. Their size is up to 100 miles long and up to 600 feet high. The one in front of Barkhan. The slope is gentle and the opposite slope is concave.