Your answer was mountain tops. people have made the same choice. Mountain tops is an excellent choice, but sorry it is not correct one. The brown areas do look like mountains but actually they are just dry ground.
The answer is a desert depression. The image you're studying is part of the Rub al Khali desert in Saudi Arabia and Oman in the Middle East. It is so dry and the sand so soft that hardly anything - not plant, not animal, not human - lives there.
The picture may look wet to you but the truth is that this part of the Rub al Khali is like a huge sink and catches any water in the area and keeps it. There isn't really much water anyway and, certainly, not enough to form a beautiful lake. What the water makes is a type of muddy sand. LANDSAT "sees" damp ground as bright blue. The white areas were once muddy sand but were dry when the LANDSAT took this picture.