[" 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."]