Which of the following are impacts of hydroelectric power plant?…

Hydroelectric projects can degrade land through submergence, deforestation and siltation (A), trigger small earthquakes as the weight of a large reservoir and changes in pore pressure stress the rocks beneath (B), release greenhouse gases such as methane from submerged vegetation decaying in the reservoir (C), and change the quality, temperature and oxygen content of water downstream (D). Smog comes from burning fossil fuels in vehicles and thermal plants, and a hydroelectric plant burns no fuel, so smog formation is not one of its impacts.