Which letter-cluster will replace the question mark (?) to complete the given series?

PORK, NQPM, LSNO, JULQ, ?

HWJS

Explanation:

PORK, NQPM, LSNO, JULQ, ?

The logic followed here is :

P → (-2) → N → (-2) → L → (-2) → J → (-2) → H

O → (+2) → Q → (+2) → S → (+2) → U → (+2) → W

R → (-2) → P → (-2) → N → (-2) → L → (-2) → J

K → (+2) → M → (+2) → O → (+2) → Q → (+2) → S

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