The three given vertices are (0٫ 4)٫(8٫ 4) and (8٫ 1). Note that the x-coordinates of two of these are both 8. The remaining x-coordinate of the fourth vertex is 0. Since the figure is a rectangle, there are two sets of parallel sides. If one side is x = 8, the opposite vertical side must be x = 0, since the remaining coordinate is 0. This side is a vertical line segment. The fourth and last vertex is at the intersection of x = 0 and y = 1; (0, 1): Answer D.
