Graph A: A uniform density curve is at y = one-fourth from negative 1 to 3. Graph B: A line goes from (negative 1, 0) to (0, one-third), is horizontal to (2, one-third), and then decreases to (3, 0). Which graph represents a density curve, and why? graph A only, because the curve is above the horizontal axis, and the area under the curve is 1 graph B only, because the curve is above the horizontal axis, and the area under the curve is 1 both graph A and graph B, because both curves are above the horizontal axis, and the areas under both curves equal 1 neither graph A nor graph B, because, even though both curves are above the horizontal axis, the area cannot be determined for graph B