Which statements prove that a quadrilateral is a parallelogram?

A - Quadrilateral DEFG has two sets of consecutive angles that are complementary.
B - Quadrilateral DEFG has one set of opposite sides that are both congruent and parallel.
C - Quadrilateral DEFG has diagonals that are congruent.
D - Quadrilateral DEFG has opposite angles that are congruent.