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

DZA, FUD, HPG, JKJ, LFM, ?

NAP

Explanation:

DZA, FUD, HPG, JKJ, LFM, ?

The logic followed here is :

D → (+2) → F → (+2) → H → (+2) → J → (+2) → L → (+2) → N

Z → (-5) → U → (-5) → P → (-5) → K → (-5) → F → (-5) → A

A → (+3) → D → (+3) → G → (+3) → J → (+3) → M → (+3) → P

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