c) No. When a 2nd derivative is equal to zero, you get no information about the graph. When f''(x) is less than 0, you have a local maximum at x. When f''(x) is greater than 0, you have a local minimum at x. However an inflection point is where the graph changes concavity. It increases, reaches a critical point, then increase further, or vice versa! Can you think of a way to find these?