Select the letter-cluster from among the given options that can replace the question mark (?) in the following series.

KRA, IQZ, ?, EOX, CNW

GPY

Explanation:

KRA, IQZ, ?, EOX, CNW

The logic followed here is :

K → (+2) → I → (+2) → G → (+2) → E → (+2) → C

R → (-1) → Q → (-1) → P → (-1) → O → (-1) → N

A → (-1) → Z → (-1) → Y → (-1) → X → (-1) → W

So, the letter-cluster that replaces the (?) to complete the series is "GPA"