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

TULG, WRPC, ZOTY, CLXU,?

FIBQ

Explanation:

TULG, WRPC, ZOTY, CLXU,?

The logic followed here is :

T → (+3) → W → (+3) → Z → (+3) → C → (+3) → F

U → (-3) → R → (-3) → O → (-3) → L → (-3) → I

L → (+4) → P → (+4) → T → (+4) → X → (+4) → B

G → (-4) → C → (-4) → Y→ (-4) → U → (-4) → Q

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