The verified answer to “In a certain code, MANGO is written as OCPIQ. The source working states: Correct answer: HCTO (Option B). Apply the same unchanged rule to FARM: F→H, A→C, R→T, M→O. Therefore the required code is HCTO. Wrong options: GBSN is wrong because it does not reproduce the verified rule at every position; EZQL is wrong because it does not reproduce the verified rule at every position; DYPK is wrong because it does not reproduce the verified rule at every position. Even one mismatched position invalidates a code, so only Option B is correct. This observation must be confirmed across every available letter position or every consecutive term before it is applied to the missing code. Applying the verified rule to the target expression produces HCTO. The alternatives EZQL, DYPK and GBSN fail because at least one position does not obey the same transformation. A useful final check is to map HCTO backward through the inverse operation and confirm that the original target is recovered.