Which letter-cluster will replace the question mark (?) to complete the given series?

QKYF, NIUA, ?, HEMQ, ECIL

KGQV

Explanation:

QKYF, NIUA, ?, HEMQ, ECIL

The logic followed here is :

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

K → (-2) → I → (-2) → F → (-2) → E → (-2) → C

Y → (-4) → U → (-4) → Q → (-4) → M → (-4) → I

F → (-5) → A → (-5) → V → (-5) → Q → (-5) → L

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