If every pair of consecutive angles of a quadrilateral are supplementary then the quadrilateral must be a parallelogram.?

If every pair of consecutive angles of a quadrilateral is supplementary, it means that the sum of each pair of adjacent angles equals 180 degrees. This implies that the opposite angles are equal, as each pair of opposite angles can be expressed as the sum of two supplementary pairs. According to the properties of quadrilaterals, if the opposite angles are equal, the quadrilateral must indeed be a parallelogram. Therefore, the condition guarantees that the quadrilateral is a parallelogram.