Complete the proof of the statement, "If a figure is a rectangle, then it must me a parallelogram". Use the diagram provided to help you. Angles A and D are supplementary [Select] transversal AD, so lines DC and AB are parallel by the [Select] Similarly, angles A and B are [Select] same side interior angles formed by transversal AB which makes lines AD and BC also parallel. Finally, ABCD must be a parallelogram because we have just proven both pairs of opposite sides are [Select]