The correct answer is option 3, "Dunes." Dunes are mounds of sand that are formed by the action of wind. They typically form in arid or desert regions where there is ample amounts of loose sand and strong winds. The wind blows the sand particles and they accumulate, forming these mounds. Dunes can vary in size, shape, and orientation depending on factors such as wind speed, direction, and the availability of sand. They are often found in vast sandy deserts like the Sahara Desert. Cliffs, option 1, are vertical or steep rock faces, and they are not formed by wind action. Cirques, option 2, are amphitheater-like depressions found at the head of a glacier or in a mountainous region, and they are not formed by wind action either. Hamadas, option 4, are rocky, barren plains found in desert regions, and they are also not formed by wind action.