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

ROM, URJ, XUG, AXD, ?

DAA

Explanation:

ROM, URJ, XUG, AXD, ?

The logic followed here is :

R → (+3) → U → (+3) → X → (+3) → A → (+3) → D  

O → (+3) → R → (+3) → U → (+3) → X → (+3) → A  

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

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