A D 15. All the vertices of quadrilateral MNPQ are located exactly 2 units from the origin on the coordinate grid below. Which argument is sufficient to prove that MNPQ is a square? The slopes of MN and OP are each 1, and the slopes of NP and MQ are each - 1. Because the product of the slopes is - 1 and the sides are perpendicular, MNPQ must be a square. O MP and NO bisect each other. MN and OP are each 2 units long. Because the diagonals bisect each other and a pair of opposite sides is congruent, MNPQ must be a square. O MN and OP are each W2 units long. The slopes of MN and OP are each 1. Because opposite sides have the same length and are parallel, MNPQ must be a square. MP and NO are each 4 units long. The diagonals are along the axes and are perpendicular. Because the diagonals are congruent and perpendicular, MNPQ must be a square.