If a pair of opposite sides of a quadrilateral are equal and parallel, it is a
Parallelogram
Given AB = DC and AB // DC
Join DB
In DABand BCA,
(i) AB = DC ….. (given)
(ii) ∠ABD = ∠CDB ….. (alternate angles)
(iii) DB = DB …….(common side)
(iv) DAB ≅ BCA ….. (SAS Postulate)
(vi) AD = BC …… (cpct)
(vii) ABCD is a parallelogram (opposite sides are equal)
Hence (D)