Expression : UPM, BWT, IDA, PKH, ? The pattern followed in each letter of the terms is : 1st letter : U (+7 letters) = B (+7 letters) = I (+7 letters) = P (+7 letters) = W 2nd letter : P (+7 letters) = W (+7 letters) = D (+7 letters) = K (+7 letters) = R 3rd letter : M (+7 letters) = T (+7 letters) = A (+7 letters) = H (+7 letters) = O Thus, missing term = WRO