The verified answer to “In a certain code, RAIN is written as AINR. How will GREEN be written in that code?” is REENG, option B. The source working states: Correct answer: REENG (Option C). Apply the same unchanged rule to GREEN: G→R, R→E, E→E, E→N, N→G. Therefore the required code is REENG. Wrong options: HSFFO is wrong because it does not reproduce the verified rule at every position; ITGGP is wrong because it does not reproduce the verified rule at every position; FQDDM is wrong because it does not reproduce the verified rule at every position. Even one mismatched position invalidates a code, so only Option C 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 REENG. The alternatives ITGGP, FQDDM and HSFFO fail because at least one position does not obey the same transformation. A useful final check is to map REENG backward through the inverse operation and confirm that the original target is recovered.