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

RAB, TDG, VGL, ? , ZMV

XJQ

Explanation:

RAB, TDG, VGL, ? , ZMV

The logic followed here is :

R → (+2) → T → (+2) → V → (+2) → X → (+2) → Z  

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

B → (+5) → G → (+5) → L → (+5) → Q → (+5) → V  

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