The question presents a coding-decoding problem where we need to identify a consistent pattern between given letter groups and then apply that pattern to a new group. This type of problem is common in logical reasoning and aptitude sections of various examinations.

Decoding the Pattern

We are provided with three examples of transformations:

• IMHO = JNIP
• IDK = JEL
• SO = TP

Our first step is to carefully analyze each of these transformations to find the rule. Let's look at the position of each letter in the English alphabet (A=1, B=2, C=3, ..., Z=26).

From the detailed analysis in the table, it is clear that a very simple and consistent pattern is being followed across all the given examples. Each letter in the original word is consistently replaced by the immediate next letter in the English alphabet. This means a uniform shift of one position forward ($\text{letter} \rightarrow \text{next letter}$).

Applying the Pattern to IDC

Now that we have successfully identified the pattern (a shift of +1 for each letter), we can apply this exact same rule to find the coded form of "IDC". We will take each letter in "IDC" and find the letter that immediately follows it in the alphabet.

• For the letter I: The letter that comes next after 'I' is J.
• For the letter D: The letter that comes next after 'D' is E.
• For the letter C: The letter that comes next after 'C' is D.

Deriving the Final Coded Word

Combining the results from applying the pattern to each letter of "IDC", we get the following transformation:

• I $\rightarrow$ J
• D $\rightarrow$ E
• C $\rightarrow$ D

Therefore, based on the established coding rule, "IDC" transforms into JED.

This type of problem emphasizes careful observation and the ability to apply a discovered rule consistently to new inputs.