The paragraph describes how nitrogen and phosphorus input causes algal blooms and oxygen depletion, affecting lake ecosystems, exemplified by the issues in Lake Erie and the Gulf of Mexico.
The paragraph that best represents the overall problem question, hypothesis, and testable solution of lake health is the one discussing how the input of nitrogen and phosphorus leads to the growth of algae, causing algal blooms and oxygen depletion, impacting the lake ecosystem and potentially leading to dead zones like those seen in Lake Erie and the Gulf of Mexico due to environmental challenges.
https://brainly.com/question/38683782