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

PGF, QJK, RMP, SPU, ?

TSZ

Explanation:

PGF, QJK, RMP, SPU, ?

The logic followed here is :

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

G → (+3) → J → (+3) → M → (+3) → P → (+3) → S

F → (+5) → K → (+5) → P → (+5) → U → (+5) → Z

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