To solve this code language problem, we must identify the pattern in which the letters of the words 'BHOPAL' and 'KANPUR' are rearranged to form 'OBHLPA' and 'NKARPU' respectively.

Let's break down the translation:

1. For 'BHOPAL' to 'OBHLPA':
   • The first and second letters are swapped: 'B' and 'O' to form 'O' and 'B'.
   • The middle letters remain unchanged: 'H' and 'L'.
   • The last letters 'PA' are swapped to become 'AP'.
   • Resulting in the sequence: 'O' + 'B' + 'H' + 'L' + 'P' + 'A' = 'OBHLPA'.
2. For 'KANPUR' to 'NKARPU':
   • The first two letters 'K' and 'A' are swapped to become 'N' and 'K'.
   • The middle letters 'N' and 'P' remain in position as 'A' and 'R'.
   • The last pair 'UR' is swapped to become 'PU'.
   • Resulting in the sequence: 'N' + 'K' + 'A' + 'R' + 'P' + 'U' = 'NKARPU'.

Identifying the above pattern, each word undergoes rearrangement where:

• The first two letters are swapped.
• The middle pair of letters (if any) remains in its position.
• The last pair of letters is swapped.

Now applying the same rules to 'INDORE':

• First two letters 'I' and 'N' are swapped to become 'N' and 'I'.
• Middle pair 'D' and 'O' remain in its position as 'D' and 'O'.
• Last pair 'R' and 'E' are swapped to become 'E' and 'R'.

This results in: I \to D, N \to I, D \to N, O \to O, R \to R, E \to E = 'DINEOR'.

The correct answer is, therefore, 'DINEOR'.