SOLUTION
When a graph, let's say y = f(x) has a point of inflection (changes from concave up to concave down), the graph of its derivative y = f '(x) has a maximum or minimum (and so changes from increasing to decreasing or decreasing to increasing respectively).
So, from this explanation, the graphs that change concavity are
Graphs B, C, D, E, J, K, M, and O.