Because think about, if your derivative goes from being negative to positive, that means your original function goes from decreasing to increasing, goes from decreasing to increasing, and so you would have a relative minimum point. And the choice that describes that, this is starting to get there, but this alone isn't enough for a relative minimum point. F is negative before x equals eight and positive after x equals eight. That's exactly what we just described. Let's see about these. F is concave up on the interval around x equals six. Well, x equals six is a little bit unrelated to that.