Your answer was the correct one, sand dunes. people have made the same choice.
You got it! They are sand dunes. In fact, they are pretty big sand dunes called star dunes. The average star dune is 1/2 to 1 mile around and 500 to 800 feet tall. The typical classroom is about 8 feet from floor to ceiling - that means that the star dunes are about 60 to 100 classrooms high! These star dunes are in the Grand Erg Oriental which is in the countries of Algeria, Tunisia and Libya in the Sahara Desert in North Africa.
Star Dunes are 1/2 to 1 mile around and are 500-800 feet tall.