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

GCB, JHE, MMH, PRK, ?

SWN

Explanation:

GCB, JHE, MMH, PRK, ?

The logic followed here is :

G → (+3) → J → (+3) → M → (+3) → P → (+3) → S

C → (+3) → H → (+3) → M → (+3) → R → (+3) → W

B → (+3) → E → (+3) → H → (+3) → K → (+3) → N

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