Step 1: Understanding the Concept:
Check for "Opposite Letter" pairs. In this system, A maps to Z, B to Y, C to X, etc. (the sum of their alphabetical positions is 27).
Step 2: Identifying the Vector of Change:
- B (2nd from start) $\leftrightarrow$ Y (2nd from end)
- E (5th from start) $\leftrightarrow$ V (5th from end)
- A (1st from start) $\leftrightarrow$ Z (1st from end)
- T (20th from start) $\leftrightarrow$ G (20th from end)
Step 3: Calculation:
Find the opposite letters for MILD:
- M (13th) $\rightarrow$ N (27 - 13 = 14)
- I (9th) $\rightarrow$ R (27 - 9 = 18)
- L (12th) $\rightarrow$ O (27 - 12 = 15)
- D (4th) $\rightarrow$ W (27 - 4 = 23)
Step 4: Final Answer:
The code for MILD is NROW. Thus, the correct option is (d).