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

CALI, ZEGO, WIBU, TMWA, ?

QQRE

Explanation:

CALI, ZEGO, WIBU, TMWA, ?

The logic followed here is :

C → (-3) → Z → (-3) → W → (-3) → T → (-3) → Q

A → (+4) → E → (+4) → I → (+4) → M → (+4) → Q

L → (-5) → G → (-5) → B → (-5) → W → (-5) → R

I → (+6) → O → (+6) → U → (+6) → A → (+6) → G

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