The correct answer is 2.5%. Explanation & Key Takeaways: • Freshwater constitutes approximately 2.5% of the total water available on Earth, but the majority is inaccessible as it is locked in glaciers, ice caps, and deep underground reserves. • Out of this freshwater, only about 0.025% is accessible for human use, which includes water in rivers, lakes, and shallow groundwater sources. • The remaining freshwater is stored in forms that are difficult to extract, such as deep aquifers or polar ice caps. • Freshwater is essential for various purposes, including drinking, agriculture, sanitation, and industrial needs, making its sustainable management a global priority. • Despite its scarcity, freshwater resources face mounting pressures from climate change, population growth, and pollution, threatening water security worldwide. Related Concepts: • Global Water Distribution: • Approximately 97.5% of Earth's water is saline and found in oceans, making it unsuitable for direct human consumption or use. • The remaining 2.5% is freshwater, primarily stored in glaciers (68.7%), groundwater (30.1%), and surface water sources like rivers and lakes (0.3%). • Freshwater Ecosystems: • Freshwater ecosystems include rivers, lakes, wetlands, and aquifers, which support a wide range of species and biodiversity. • These ecosystems play a vital role in regulating the Earth's water cycle and maintaining ecological balance. • Water Scarcity: • Approximately 1.2 billion people worldwide face physical water scarcity, while another 1.6 billion face economic water shortages due to lack of infrastructure. • Water scarcity is exacerbated by factors such as climate change, over-extraction of water resources, and pollution. • United Nations Sustainable Development Goal (SDG) 6: • SDG 6 aims to ensure availability and sustainable management of water and sanitation for all by 2030. • It emphasizes universal access to safe and affordable drinking water and the protection of water-related ecosystems.