Who can answer a few geographical questions? Thank you.

1. Cave dwellings are traditional dwellings on the Loess Plateau, because of the uprightness and hygroscopicity of loess, while the native soil in the south is mainly red soil, which does not meet the above conditions.

2. Weihe River is a first-class tributary of the Yellow River, and Jinghe River is a second-class tributary of the Yellow River, which flows into Weihe River near Xianyang. Weihe river basin is the birthplace of Qin dynasty, with a long history, concentrated human activities and serious vegetation destruction. The result of vegetation destruction is soil erosion and the increase of river sediment concentration. In addition to the above reasons, there are natural reasons, such as being located inland, the water vapor is difficult to reach and the climate is dry. So the river is muddy. The reason for the obvious difference is human factors.

3. Governance is necessary, but it is difficult, which makes the ecosystem easy to recover and difficult to recover. The more complex the ecosystem, the more difficult it is to recover.