Fill the blank in the middle of the series or end of the series:
OLT, NNS, MPR, LRQ, _______1st letter: Decrease by - 1
O - 1→ N – 1 → M - 1 → L – 1 → K
2nd letter: increase by + 2
L + 2 → N + 2→ P + 2 → R + 2 → T
3rd letter: Decrease by - 1
T - 1→ S – 1 → R - 1 → Q – 1 → P
Hence, “KTP” will come next.




