Quadrilaterals

The quadrilateral formed by joining the mid-points of the sides of a quadrilateral
PQRS, taken in order, is a rhombus, if
(A) PQRS is a rhombus
(B) PQRS is a parallelogram
(C) diagonals of PQRS are perpendicular
(D) diagonals of PQRS are equal.