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 + 5 = 2nd letter and 2nd letter + 5 = 3rd letter

Now, we check each options.

Option (a): NSX (Follow)

N + 5 = S, S + 5 = X

Option (b): INS (Follow)​

I + 5 = N, N + 5 = S

Option (c): LOV (Not Follow)​

L + 5 $$\neq$$ O, O + 5 $$\neq$$ V​

Option (d): GLQ (Follow)​

G + 5 = L, L + 5 = Q

Thus, correct option is (c).