The quadrilateral ABCD be a parallelogram if ∠D + ∠B = 180°,
it should also fulfilled some conditions which are:
(a) The sum of the adjacent angles should be 180°.
(b) Opposite angles must be equal.
(ii) No, opposite sides should be of the same length.
In this, AD ≠ BC
(iii) No, opposite angles should be of same measures.
In this, ∠A ≠ ∠C