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