What does that -11 refer to? -11 questions allowed for a 170?

I've noticed this too, and agree: it's not a major problem, but it's kind of annoying. I'd love to see the radio buttons moved off the graph.

Thanks for your response! I am not sure that you're right about your negation of A. I negated it thus: "It is not the case that the most important environmental problems involve endangered species other than large mammals," or, "The most important environmental problems do not involve endangered species other than large mammals."

If we accept that negation as a premise, it's possible for the category of "the most important environmental problems" to be occupied only by problems that do not involve endangered animals at all. Like space debris, maybe. Whether there are actually any real world problems that do not involve endangered species should not matter. Let's assume that space debris is one.

In that case the conclusion of the argument could still stand. Of course publicity campaigns for endangered animals would be unlikely to have much of an impact on the problem of space debris.

What I failed to understand (but now think I do) is that in the above scenario the relationship between and premise of the argument and its conclusion would be wrecked. What relevance could microorganisms possibly have to the space debris problem? The fact that the argument's conclusion is incidentally allowed to remain intact is irrelevant: the heart of the argument (the connection between P and C) has been destroyed.

So without A as a premise the argument fails, even in my (admittedly pretty contrived) possible world.

Does that sound right? Thanks for engaging. It's helpful to tease this stuff out with other people.

I'm having trouble understanding how A is a necessary assumption. What if none of the most important environmental problems involve endangered species at all?