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

TX, ZD, FJ, LP, ?

RV

Explanation:

TX, ZD, FJ, LP, ?

The logic followed here is :

T → (+6) → Z → (+6) → F → (+6) → L → (+6) → R  

X → (+6) → D → (+6) → J → (+6) → P → (+6) → V  

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