From the given points, AB=√12+12+52 =√27 BC=√02+22+42 =√20 CD=√12+12+52 =√27 And DA=√02+22+42 =√20 These shows, AB=CD and BC=DA Now, AC=√12+32+12 =√11 And, DB=√12+12+92 =√83 It means, AC≠DB Hence, A,B,C and D forms a parallelogram.