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

AY, BX, ?, DV, EU, FT

CW

Explanation:

AY, BX, ?, DV, EU, FT

The logic followed here is :

A → (+1) → B → (+1) → C → (+1) → D → (+1) →  E → (+5) → F

Y → (-1) → X → (-1) → W → (-1) → V → (-1) → U → (+5) → T

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