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

ABCD, YZEF, WXGH, UVIJ, ?

STKL

Explanation:

ABCD, YZEF, WXGH, UVIJ, ?

The logic followed here is :

A→ (-2) → Y → (-2) → W → (-2) → U → (-2) → S

B → (-2) → Z → (-2) → X → (-2) → V → (-2) → T

C→ (+2) → E → (+2) → G → (+2) → I → (+2) → K

D → (+2) → F → (+2) → H → (+2) → J → (+2) → L

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