Test students' understanding of how human activities alter the nitrogen cycle and drive freshwater eutrophication. Include major sources of reactive nitrogen (fertilizers, fossil fuel combustion, wastewater), pathways into aquatic systems (runoff, leaching, atmospheric deposition), key biogeochemical processes (nitrification, denitrification), ecological consequences (algal blooms, hypoxia, biodiversity loss), basic interpretation of nutrient/DO data, and common mitigation strategies (BMPs, riparian buffers, improved wastewater treatment).