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

EFY, FID, GLI, HON, IRS, ?

JUX

Explanation:

EFY, FID, GLI, HON, IRS, ?

The logic followed here is :

E → (+1) → F → (+1) → G → (+1) → H → (+1) → I → (+1) → J

F → (+3) → I → (+3) → L → (+3) → O → (+3) → R → (+3) → U

Y → (+5) → D → (+5) → I → (+5) → N → (+5) → S → (+5) → X

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