In a certain code language, 'MAIN' is written as 'OHBL' and 'MAIL' is written as 'MHBL'. How will 'MANY’ be written in that language?

Correct — C.

Rule: reverse the word first, then shift the letters +1, −1, +1, −1.

MAIN reversed is N I A M.
N+1 = O, I−1 = H, A+1 = B, M−1 = L → OHBL ✓

MAIL reversed is L I A M.
L+1 = M, I−1 = H, A+1 = B, M−1 = L → MHBL ✓

MANY reversed is Y N A M.
Y+1 = Z, N−1 = M, A+1 = B, M−1 = L → ZMBL → option (c).

Why the others are wrong

• (a)
  ZBLM — ZBLM holds the right four letters in the wrong order. The reversal happens before the shifts, so the letter after Z is N−1 = M, not B.
• (b)
  ZMLB — ZMLB swaps the last two letters. The third letter of the reversed word is A and A+1 = B, so B comes third, ahead of M−1 = L.
• (d)
  ZLMB — ZLMB puts L second. The second letter of the reversed word is N and the second shift is −1, which gives M; L is the last letter, from M−1.

Letter-coding items are settled by a routine: write the alphabet positions, compare code and word position by position, and if that yields nothing, try the word reversed.

MAIN and OHBL look unrelated until the reversal. Set N I A M above O H B L and the gaps read +1, −1, +1, −1.

The second given pair is a check, not decoration. MAIN and MAIL differ only in their last letter, and their codes OHBL and MHBL differ only in the first position — exactly what a reversal predicts.

Key facts

• MAIN reversed is NIAM, and the shifts +1, −1, +1, −1 give OHBL.
• MAIL reversed is LIAM, and the same shifts give MHBL.
• MANY reversed is YNAM, and the same shifts give ZMBL.

Common traps

• Shifting first and reversing afterwards, which is a different operation because the shifts depend on position
• Seeing +1 on the first letter and shifting all four the same way

No directly related past PYQ was found.