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

PND, QKI, RHN, SES, ?

TBX

Explanation:

PND, QKI, RHN, SES, ?

The logic followed here is :

P → (+1) → Q → (+1) → R → (+1) → S → (+1) → T

N → (-3) → K → (-3) → H → (-3) → E → (-3) → B 

D → (+5) → I → (+5) → N → (+5) → S → (+5) → X

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