Based on the English alphabetical order, three of the following four letter-clusters are alike in a certain way and thus form a group. Which letter-cluster DOES NOT belong to that group?
(Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)​

Logic: 1st letter + 4 = 2nd letter, 2nd letter + 3 = 3rd letter and 3rd letter + 6 = 4th letter

Now, we check each options.

Option (a): NRUA (Follow)

N + 4 = R, R + 3 = U, U + 6 = A

Option (b): GKNT (Follow)​

G + 4 = K, K + 3 = N, N + 6 = T

Option (c): DGKQ (Not Follow)​

D + 4 $$\neq$$​ G, G + 3 $$\neq$$​ K, K + 6 = Q

Option (d): QUXD (Follow)​

Q + 4 = U, U + 3 = X, X + 6 = D

Thus, correct option is (c).