Which letter-cluster will replace the question mark (?)

Solution

The logic followed here is: The 1st letter of each letter-cluster is the seventh succeeding letter of the 1st letter of the previous letter-cluster, the 2nd letter of each letter-cluster is the third preceding letter of the 2nd letter of the previous letter cluster, the 3rd letter of each letter-cluster is the fourth preceding letter of the 3rd letter of the previous letter-cluster and the 4 th letter of each letter-cluster is the fifth preceding letter of the 4th letter of the previous letter cluster as per the English alphabetical series 1st letter of each letter cluster, G + 7 = N, N + 7 = U, U + 7 = B, B + 7 = I, I + 7 = P U - 3 = R, R - 3 = O, O - 3 = L, L - 3 = I, I - 3 = F F - 4 = B, B - 4 = X, X - 4 = T, T - 4 = P, P - 4 = L N - 5 = I, I - 5 = D, D - 5 = Y, Y - 5 = T, T - 5 = O