Four letter-clusters have been given, out of which three are alike in some manner and one is different. Select the odd letter cluster.

GHJMP

THE LOGIC;

1) GHJMP,

G → (+1) → H → (+2) → J → (+3) → M → (+3) → P

2) ABDGK,

A → (+1) → B → (+2) → D → (+3) → G → (+4) → K

2) BCEHL,

B → (+1) → C → (+2) → E → (+3) → H → (+4) → L

4) NOQTX,

N → (+1) → O → (+2) → Q → (+3) → T → (+4) → X

Thus, GHJMP is the odd one.