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

XMT, ENA, LOH, SPO, ?

ZQV

Explanation:

XMT, ENA, LOH, SPO, ?

The logic followed here is :

X → (+7) → E → (+7) → L → (+7) → S → (+7) → Z

M → (+1) → N → (+1) → O → (+1) → P → (+1) → Q 

T → (+7) → A → (+7) → H → (+7) → O → (+7) → V

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