Final answer:
Mountain ranges are not permanent and are constantly being broken down by erosion caused by factors like water and ice. They are formed by tectonic plate activity, where continental masses collide and the pressure causes the crust to buckle and fold, raising some rocks to form mountains. Therefore, the correct answer is (e) are constantly being broken down by erosion.
Step-by-step explanation:
Mountain ranges are not permanent features of Earth's surface. They are constantly being broken down by erosion caused by factors like water and ice. Once a mountain range is formed by the upthrust of the crust, its rocks are subject to erosion, resulting in changes to the landscape over time.
The formation of mountain ranges is mainly caused by tectonic plate activity. When two continental masses collide, they push against each other under pressure, causing Earth's crust to buckle and fold. This process raises some rocks to form mountains. Examples of mountain ranges formed by plate activity include the Alps, which are a result of the African plate colliding with the Eurasian plate.