If IMHO = JNIP; IDK = JEL; and SO = TP, then IDC = __________.

The correct option is JED.

To solve this letter-coding puzzle, we need to analyze the relationship between the original words and their coded counterparts. Let us look at the alphabetical position shifts for each letter:

First, let us examine the word IMHO which is coded as JNIP:

• $I\to J$ (Shifted forward by 1 position: $I+1=J$)

• $M\to N$ (Shifted forward by 1 position: $M+1=N$)

• $H\to I$ (Shifted forward by 1 position: $H+1=I$)

• $O\to P$ (Shifted forward by 1 position: $O+1=P$)

Next, let us verify this rule with the second pair, IDK coded as JEL:

• $I\to J$ (Shifted forward by 1 position: $I+1=J$)

• $D\to E$ (Shifted forward by 1 position: $D+1=E$)

• $K\to L$ (Shifted forward by 1 position: $K+1=L$)

Similarly, for SO coded as TP:

• $S\to T$ (Shifted forward by 1 position: $S+1=T$)

• $O\to P$ (Shifted forward by 1 position: $O+1=P$)

From these examples, it is clear that the code shifts each letter of the word forward by exactly 1 position in the English alphabet.

Now, let us apply this pattern to the word IDC to find the missing code:

• First letter: $I+1=J$

• Second letter: $D+1=E$

• Third letter: $C+1=D$

Putting these letters together gives JED. Thus, the coded form of IDC is JED.