The verified answer to “In a certain code, MATH is written as PDWK. How will MOON be written in that code?” is PRRQ, option D. The source working states: Correct answer: PRRQ (Option A). Apply the same unchanged rule to MOON: M→P, O→R, O→R, N→Q. Therefore the required code is PRRQ. Wrong options: NPPO is wrong because it does not reproduce the verified rule at every position; OQQP is wrong because it does not reproduce the verified rule at every position; LNNM is wrong because it does not reproduce the verified rule at every position. Even one mismatched position invalidates a code, so only Option A 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 PRRQ. The alternatives NPPO, OQQP and LNNM fail because at least one position does not obey the same transformation. A useful final check is to map PRRQ backward through the inverse operation and confirm that the original target is recovered.