I think the only real difficulty for me on this question was realizing I should diagram. As soon as I did I saw the flaw, unfortunately, I had already submitted the wrong answer, Lol. Anyhow, does anyone have any tips for identifying when to diagram reasoning flaw questions? Or should that just be the default?

couldn't you rule out A because it's talking about Sewage pollution when the passage only talks about nutrient rich sewage pollution?