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

ACL, DFO, GIR, JLU, MOX, ?

PRA

Explanation:

ACL, DFO, GIR, JLU, MOX, ?

The logic followed here is :

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

C → (+3) → F → (+3) → I → (+3) → L → (+3) → O → (+3) → R

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

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