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 letters + 3 = 2nd letters, 2nd letters - 2 = 3rd letters 

Option (a): ZCA

Z + 3 = C, C - 2 = A

Option (b): GJH

G + 3 = J, J - 2 = H

Option (c): MPD

M + 3 = P, P - 12 = D

Option (d): LOM

L + 3 = O, O - 2 = M

There are only three options A, B, D which are following the same logic: 

So, the correct odd one out is MPD.​

Thus, the correct option is (c) MPD.