I chose E, but for a second was tempted with B. I ended up ruling B out because of D. Although the levels may have been lower prior to to 85, it doesn't mean they were sufficient to even lower the risk of airborne illness so we can't, for certain, say that the risk is now higher. Idk if that makes sense but that's how I got there.

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?