A quadrilateral has vertices, taken in order, at A(−2, −1), B(1, 0), C(4, 3) and D(1, 2). Which description of this quadrilateral is correct?

AB = √$(3^2+1^2)=$ √10 and DC = √$(3^2+1^2)=$ √10; BC = √$(3^2+3^2)=$ √18 and AD = √$(3^2+3^2)=$ √18. Opposite sides are equal, and the vector from A to B equals the vector from D to C, so it is a parallelogram. It is not a rhombus because √10 ≠ √18, and it is not a rectangle because the diagonals AC = √52 and BD = 2 are unequal.