The correct answer is option 4: Deserts. Mushroom Rocks are distinct landforms that are commonly found in desert regions. They are also known as rock pedestals or hoodoos. Mushroom Rocks are formed through a process called differential weathering, where softer rock erodes faster than harder rock layers. In deserts, the dry and arid conditions contribute to the formation of Mushroom Rocks as the wind and occasional rain erosion gradually carve out these unique mushroom-shaped formations. The hard capstone on top protects the softer rock beneath, creating the characteristic shape. While river valleys, mountain tops, and coastal areas may have their own unique landforms, Mushroom Rocks are more commonly associated with deserts.