Which of the following statements is not necessarily true?
(I) A quadrilateral is a parallelogram if its diagonals bisect each other.
(II) If the diagonals of a quadrilateral are equal, then it is a rectangle.
(III) If the diagonals of a quadrilateral intersect at right angles, then it is a rhombus.
(IV) A rectangle, a square and a rhombus are special types of parallelogram
(A) I
(B) II
(C) III
(D) More than one of the above
(E) None of the above
