Based on the position in the English alphabetical order, three of the following letterclusters are alike in some manner and one is different. Select the odd letter-cluster.

QUXZ

THE LOGIC;

1) QUXZ,

Q → (+4) → U → (+3) → X → (+2) → Z

2) GKOQ,

G → (+4) → K → (+4) → O → (+2) → Q

3) AEIK,

A → (+4) → E → (+4) → I → (+2) → K

4) KOSU,

K → (+4) → O → (+4) → S → (+2) → U

Thus, QUXZ is the odd one.