Which of the following letter-clusters will replace the question mark (?) in the given series?

LAT, NDR, PGP, ?, TML

RJN

Explanation:

LAT, NDR, PGP, ?, TML

The logic followed here is :

L → (+2) → N → (+2) → P → (+2) → R → (+2) → T → (+2) 

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

T → (-2) → R → (-2) → P → (-2) → N → (-2) → L → (-2) 

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