Select the letter-cluster that can replace the question mark (?) in the following series.
FIY, HLD, JOI, LRN, NUS, ?

Given that FIY, HLD, JOI, LRN, NUS,?

We know that Alphabet position A=1, B=2, C=3 ........ Z=26.

the given alphabet series represents in the form of alphabet position 

6 9 25, 8 12 4, 10 15 9, 12 18 14, 14 21 19, ?

from the above line, the series going on first is increasing  2 positions for next, second is increasing  3 positions for next and third is increasing 5 positions to next 

, therefore ? = 16 24 24 (next series element ) 

? = P X X  (16 24 24) Ans