Opposite Letter Coding

Each letter is coded by its opposite letter in the alphabet (sum of positions = 27): H (8) $\leftrightarrow$ S (19) A (1) $\leftrightarrow$ Z (26) N (14) $\leftrightarrow$ M (13) D (4) $\leftrightarrow$ W (23)

Applying same logic to MILK: M (13) $\rightarrow$ N (14) I (9) $\rightarrow$ R (18) L (12) $\rightarrow$ O (15) K (11) $\rightarrow$ P (16)

Code = NROP.

Hence, Option C is correct.