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 is the letter-cluster that DOES NOT belong to that group?
(Note: The odd man out is not based on the number of consonants/vowels or their position in the letter-cluster.)

Correct option is B

Logic - The pattern follows: +3, +4
MPT → M (13), P (16), T (20)
M + 3 = P, P + 4 = T
The pattern follows: +3, +4
ACG → A (1), C (3), G (7)
A + 2 = C, C + 4 = G
The pattern follows: +2, +4
DGK → D (4), G (7), K (11)
D + 3 = G, G + 4 = K
The pattern follows: +3, +4
HKO → H (8), K (11), O (15)
H + 3 = K, K + 4 = O

Since ACG follows a different pattern (+2, +4 instead of +3, +4), it is the odd one out.