Based on the 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 A

Logic::
All except option (a) follow the same pattern.
The position of the second letter is 3 more than the first letter.
The position of the third letter is 4 more than the second letter.
Explanation:
ILO → I + 3 = L; L + 3 = O
NQU → N + 3 = Q; Q + 4 = U
DGK → D + 3 = G; G + 4 = K
JMQ → J + 3 = M; M + 4 = Q
From the analysis, we can see:
In options, (b), (c), and (d), the letters in the letters cluster follow the same pattern.
In option (a), the letters in the letter cluster do not follow the same pattern.
Therefore, the odd option is (a), ILO.