A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.

RCMG, VWUW, ZQCM, DKKC, ?

HESS

Explanation:

RCMG, VWUW, ZQCM, DKKC, ?

The logic followed here is :

R → (+4) → V → (+4) → Z → (+4) → D → (+4) → H

C → (-5) → W → (-6) → Q → (-6) → K → (-6) → E 

M → (+8) → U → (+8) → C → (+8) → K → (+8) → S

G → (-10) → W → (-10) → M → (-10) → C → (-10) → S

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