The figure shows a quadrilateral PQRS having equal sides and opposite sides parallel. The diagonals PR and QS intersect perpendicularly at O, Which of the f...

Since PQRS is a quadrilateral with equal sides and opposite sides parallel, it must be a parallelogram. Since PR and QS are diagonals of this parallelogram and intersect perpendicularly at O, O is the midpoint of both PR and QS. Therefore, |PO|=|RO|. If PQR is an equilateral triangle, then PQ=QR=RP, which means that PQRS would be a rhombus (a special case of a parallelogram with all sides equal), not just a parallelogram. This contradicts the given information, so option (B) cannot be correct. If PQRX is a parallelogram, then PQ and RX are parallel and PQ=RX because PQRS is a parallelogram with opposite sides parallel and equal in length. This would mean that the diagonals PR and QS intersect at the midpoint of PQ and RX, not perpendicularly. This contradicts the given information that PR and QS intersect perpendicularly at O, so option (C) cannot be correct. There are no conditions given about the symmetry of the quadrilateral PQRS, so option (D) may or may not be correct. The presence or absence of lines of symmetry does not contradict any of the given information or the other options. Therefore, the statement that cannot be correct is option (B), "PQR is an equilateral triangle," since it contradicts the given information that PQRS is a parallelogram with equal sides and opposite sides parallel.