Andy is studying a quadrilateral with the vertices A(6,1).B (8,2).C(9,4), and D(7,3). Which statement explains how Andy could prove what kind of quadrilateral this is?

A. find the slopes of the pairs of opposite sides to show that the figure is a parallelogram

B. find the slopes of the pairs of opposite sides to show that the quadrilateral is a rectangle

C. find the lengths of the diagonals to show that the quadrilateral is a parallelogram

D. find the lengths of the diagonals to show that the quadrilateral is a rectangle