Let's go through the answer choices one at a time.
Choice A represents an increasing interval since the graph goes uphill as we move from left to right. The line through the points (-2, f(-2)) and (-1.5, f(-1.5)) has a positive slope. We can rule out choice A.
Choice B is a similar story to choice A. The graph goes uphill when we move from x = -1 to x = 0, so the graph is increasing on the interval -1 < x < 0. We can rule out choice B.
In contrast, choice C is a decreasing interval. Going from x = 0 to x = 1 has us move downhill. Choice C is the only answer.
Choice D is false because choice C was shown to be true.
