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.)

Correct option is B

Let’s check the options:
Logic: 1st letter − 4 = 2nd letter, 2nd letter + 3 = 3rd letter.

Option A: LHK
L − 4 = H
H + 3 = K
Option B: OKM
O − 4 = K
K + 3 ≠ M (it gives N) —  Pattern not follow.
Option C: UQT
U − 4 = Q
Q + 3 = T
Option D: RNQ
R − 4 = N
N + 3 = Q
Only OKM does not follow the pattern.
Thus, the correct option is (B) OKM.